Stator and rotor-stator structures for electrodynamic machines

ABSTRACT

Embodiments of the invention relate generally to electric motors, alternators, generators and the like, and more particularly, to stator structures and rotor-stator structures for motors that can be configured to, for example, reduce detent.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation and claims the benefit of U.S.Nonprovisional application Ser. No. 13/006,855, filed on Jan. 14, 2011,which is a Continuation and claims the benefit of U.S. Nonprovisionalapplication Ser. No. 11/925,661, filed on Oct. 26, 2007, which claimsthe benefit of U.S. Nonprovisional application Ser. No. 11/255,404,filed on Oct. 20, 2005, which claims the benefit of U.S. Provisionalapplication Ser. No. 60/622,258, filed on Oct. 25, 2004, all of whichare hereby incorporated by reference. Further, this application herebyincorporates by reference the following: U.S. Nonprovisional applicationSer. No. 11/707,817, entitled “Field Pole Members and Methods of FormingSame for Electrodynamic Machines,” published on Sep. 6, 2007 as U.S.Publication No. 20070205675 A1.

BRIEF DESCRIPTION OF THE INVENTION

Embodiments of the invention relate generally to electric motors,alternators, generators and the like, and more particularly, to statorstructures and rotor-stator structures for motors that can be configuredto, for example, reduce detent.

BACKGROUND OF THE INVENTION

Detent, which is also known as “cogging torque” or “detent torque,” is aperiodic torque created in an electro-dynamic structure that co-axiallyintegrates high permeability elements, such as field poles, into astator structure, which, in turn, is formed with permanent magnets in arotor structure. When either structure is rotated with respect to theother, a periodic varying torque can be created because the magnetstructure prefers to align centered on the high permeability elementsrather than at the intervening field pole gaps of air between the fieldpole elements. This detent torque can be created by the portion of thearea of the magnet that is not immediately facing the field pole shoe.Each incremental area of the face of the magnet that is facing an gapbetween the field pole shoes is then attracted to the nearest surface ofan adjacent field pole of high permeability, thus creating anincremental torque in that direction. The resulting detent torque can beviewed as the summation of the incremental torques over all the areasnot facing a high permeability region in the entire interface regionbetween the stator and rotor structure. The magnitude of this varyingdetent torque increases as the gap between field. pole elements canincrease because a greater portion of the magnet area is in the gapbetween field poles. While it is desirable to minimize detent torque,decreasing the field pole gap between field pole elements haslimitations because flux leakage between field poles increases.

In view of the foregoing, it would be desirable to provide stator androtor-stator structures that minimize the drawbacks of conventionalmotors and generators to reduce detent, among other things.

SUMMARY OF THE INVENTION

Embodiments of the invention relate generally to electric motors,alternators, generators and the like, and more particularly, to statorstructures and rotor-stator structures for motors that can be configuredto, for example, reduce detent. In one example, a stator structure forelectrodynamic machines can include field pole members that are arrangedcoaxial to an axis of rotation, which, in turn, can include a firstfield pole member and a second field pole member. In at least oneinstance, the second field pole member can be oriented with respect tothe first field pole member to form an overlap portion. In oneembodiment, the overlap portion can be configured to include a planethat includes the axis of rotation. In another embodiment, the secondfield pole member can be positioned to modify the effects of detent.

BRIEF DESCRIPTION OF THE FIGURES

The various embodiments of the invention are more fully appreciated inconnection with the following detailed description taken in conjunctionwith the accompanying drawings, in which:

FIG. 1 exemplifies commonly-used stator and rotor structures implementedin a traditional electric motor;

FIG. 2A is an exploded view of exemplary rotor-stator structureimplementing cylindrical magnets, according to one embodiment of thepresent invention;

FIG. 2B is an exploded view of an exemplary rotor-stator structure inwhich the magnets are conical in shape, according to one embodiment ofthe present invention;

FIG. 3 depicts an end view for the rotor-stator structure of FIG. 2Bwithout a magnet to illustrate the orientation of the pole faces thatare configured to interact via an air gap with a confronting magneticsurface of a conical magnet, according to one embodiment of the presentinvention;

FIG. 4 depicts another end view for the rotor-stator structure of FIG.2B illustrating a conical magnet positioned adjacent to pole faces inaccordance with an embodiment of the present invention;

FIGS. 5A and 5B depict sectional views illustrating an exemplarymagnetic flux path, according to at least one embodiment of the presentinvention;

FIG. 5C depicts an example of a second flux path exiting a pole face ofa stator member generating an ampere-turn magnetic flux, according toone embodiment of the present invention;

FIG. 5D depicts an example of a second flux path(s) entering a pole faceof an active field pole member that originally generated the ampere-turnmagnetic flux of FIG. 5C, according to one embodiment of the presentinvention;

FIGS. 5E and 5F depict sectional views illustrating an exemplarymagnetic flux path in another rotor-stator structure, according to anembodiment of the present invention;

FIGS. 6A and 6B illustrate an end view of another exemplary rotor-statorstructure, according to another embodiment of the present invention;

FIG. 6C depicts a partial sectional view of the rotor-stator structureof FIGS. 6A and 6B, according to one embodiment of the presentinvention;

FIGS. 7A to 7E illustrate examples of implementations of field polemembers, according to various embodiments of the present invention;

FIG. 8 illustrates another exemplary field pole member having skewedpole faces, according to a specific embodiment of the present invention;

FIGS. 9A to 9P illustrate examples of other-shaped permanent magnetsthat can be implemented in an exemplary rotor-stator structure,according to various embodiments of the present invention;

FIG. 10 shows a multiple pole magnet, according, to an embodiment of thepresent invention;

FIGS. 11A to 11C depict other examples rotor-stator structures inaccordance with various embodiments of the present invention;

FIGS. 12A to 12D illustrate another rotor-stator structure thatimplements cylindrical magnets in accordance with various embodiments ofthe present invention;

FIGS. 13A to 13D illustrate examples of other rotor-stator structuresthat implement only one magnet in accordance with various embodiments ofthe present invention;

FIGS. 14 and 15 depict examples of implementations of more than twomagnets in accordance with various embodiments of the present invention;

FIG. 16 depicts an alternative implementation of a rotor-statorstructure having skewed orientations for its field pole members inaccordance with one embodiment of the present invention;

FIGS. 17A and 17B illustrate an example of a field pole member accordingto a specific embodiment of the present invention;

FIG. 18A depicts air gaps having various degrees of uniformity,according to at least one embodiment of the present invention;

FIG. 18B depicts the configurability of air gaps according toembodiments of the present invention;

FIG. 19 is a cross-sectional view illustrating yet another general fieldpole member configuration in accordance with yet another embodiment ofthe present invention;

FIG. 20 illustrates an exemplary flux line to represent an instance ofmagnetic flux between pole faces of a field pole member, according toone embodiment of the present invention;

FIG. 21A illustrates an example of one implementation of an arrangementof field pole members to form a stator structure for electrodynamicmachines, according to at least one embodiment of the invention;

FIG. 21B illustrates examples of various implementations of field polemembers to form various stator structures for electrodynamic machines,according to various embodiments of the invention;

FIG. 21C depicts approximate detent torque amplitudes as a function ofvarious rotation angles for the field pole arrangements shown in FIG.21B, according to at least one embodiment of the invention;

FIG. 21D illustrates an example of a field pole arrangement that canfacilitate the distribution of incremental magnet elements overadditional rotation angles, according to at least one embodiment of theinvention;

FIG. 21E depicts attributes that can influence detent reduction by astator structure, according to various embodiments of the invention;

FIG. 22 depicts an example of a conical magnet that a stator structurecan be configured to confront, according to at least one embodiment ofthe invention;

FIG. 23 illustrates an example of an implementation of field polemembers for forming a stator structure, according to at least oneembodiment of the invention;

FIG. 24 illustrates an example of another implementation of field polemembers for forming a stator structure, according to another embodimentof the invention;

FIG. 25 is a perspective view of a stator structure for electrodynamicmachines, according to one embodiment of the invention;

FIG. 26 illustrates an example of yet another implementation of fieldpole. members for forming a stator structure, according to yet anotherembodiment of the invention; and

FIG. 27 is a perspective view of a stator structure for electrodynamicmachines, according to one embodiment of the invention.

Like reference numerals refer to corresponding parts throughout theseveral views of the drawings. Note that most of the reference numeralsinclude one or two left-most digits that generally identify the figurethat first introduces that reference number.

DETAILED DESCRIPTION Definitions

The following definitions apply to some of the elements described withrespect to some embodiments of the invention. These definitions maylikewise be expanded upon herein.

As used herein, the term “air gap” refers to a space, or a gap, betweena magnet surface and a confronting pole face. Such a space can bephysically described as a volume bounded at least by the areas of themagnet surface and the pole face. An air gap functions to enablerelative motion between a rotor and a stator, and to define a fluxinteraction region. Although an air gap is typically filled with air, itneed not be so limiting.

As used herein, the term “back-iron” commonly describes a physicalstructure (as well as the materials giving rise to that physicalstructure) that is often used to complete an otherwise open magneticcircuit. In particular, back-iron structures are generally used only totransfer magnetic flux from one magnetic circuit element to another,such as either from one magnetically permeable field pole member toanother, or from a magnet pole of a first magnet to a magnet pole of asecond magnet, or both, without an intervening ampere-turn generatingelement, such as coil, between the field pole members or the magnetpoles. Furthermore, back-iron structures are not generally formed toaccept an associated ampere-turn generating element, such as one or morecoils.

As used herein, the term “coil” refers to an assemblage of successiveconvolutions of a conductor arranged to inductively couple to amagnetically permeable material to produce magnetic flux. In someembodiments, the term “coil” can be described as a “winding” or a “coilwinding.” The term “coil” also includes foil coils (i.e., planar-shapedconductors that are relatively flat).

As used herein, the term “coil region” refers generally to a portion ofa field pole member around which a coil is wound.

As used herein, the term “core” refers to a portion of a field polemember where a coil is normally disposed between pole shoes and isgenerally composed of a magnetically permeable material for providing apart of a magnetic flux path.

As used herein, the term “field pole member” refers generally to anelement composed of a magnetically permeable material and being,configured to provide a structure around which a coil can be wound(i.e., the element is configured to receive a coil for purposes ofgenerating magnetic flux). In particular, a field pole member includes acore (i.e., core region) and at least one pole shoe, each of which isgenerally located near a respective end of the core. Without more, afield pole member is not configured to generate ampere-turn flux. Insome embodiments, the term “field pole member” can be describedgenerally as a “stator-core.”

As used herein, the term “active field pole member” refers to anassemblage of a core, one or more coils, and at least two pole shoes. Inparticular, an active field pole member can be described as a field polemember assembled with one or more coils for selectably generatingampere-turn flux. In some embodiments, the term “active field polemember” can he described generally as a “stator-core member.”

As used herein, the term “ferromagnetic material” refers to a materialthat generally exhibits hysteresis phenomena and whose permeability isdependent on the magnetizing force. Also, the term “ferromagneticmaterial” can also refer to a magnetically permeable material whoserelative permeability is greater than unity and depends upon themagnetizing force.

As used herein, the term “field interaction region” refers to a regionwhere the magnetic flux developed from two or more sources interactvectorially in a manner that can produce mechanical force and/or torquerelative to those sources. Generally, the term “flux interaction region”can be used interchangeably with the term “field interaction region.”Examples of such sources include field pole members, active field polemembers, and/or magnets, or portions thereof. Although a fieldinteraction region is often referred to in rotating machinery parlanceas an “air gap,” a field interaction region is a broader term thatdescribes a region in which magnetic flux from two or more sourcesinteract vectorially to produce mechanical force and/or torque relativeto those sources, and therefore is not limited to the definition of anair gap (i.e., not confined to a volume defined by the areas of themagnet surface and the pole face and planes extending from theperipheries between the two areas). For example, a field interactionregion (or at least a portion thereof) can be located internal to amagnet.

As used herein, the term “generator” generally refers to anelectrodynamic machine that is configured to convert mechanical energyinto electrical energy regardless of, for example, its output voltagewaveform. As an “alternator” can be defined similarly, the termgenerator includes alternators in its definition.

As used herein, the term “magnet” refers to a body that produces amagnetic field externally unto itself. As such, the term magnet includespermanent magnets, electromagnets, and the like. The term magnet canalso refer to internal permanent magnets (“IPMs”), surface mountedpermanent magnets (“SPMs”), and the like.

As used herein, the term “motor” generally refers to an electrodynamicmachine that is configured to convert electrical energy into mechanicalenergy.

As used herein, the term “magnetically permeable” is a descriptive termthat generally refers to those materials having a magnetically definablerelationship between flux density (“B”) and applied magnetic field(“H”). Further, “magnetically permeable” is intended to be a broad termthat includes, without limitation, ferromagnetic materials such ascommon lamination steels, cold-rolled-grain-oriented (CRGO) steels,powder metals, soft magnetic composites (“SMCs”), and the like.

As used herein, the term “pole face” refers to a surface of a pole shoethat faces at least a portion of the flux interaction region (as well asthe air gap), thereby forming one boundary of the flux interactionregion (as well as the air gap). In some embodiments, the term “poleface” can be described generally as including a “flux interactionsurface.” in one embodiment, the term “pole face” can refer to a “statorsurface.”

As used herein, the term “pole shoe” refers to that portion of a fieldpole member that facilitates positioning a pole face so that itconfronts a rotor (or a portion thereof), thereby serving to shape theair gap and control its reluctance. The pole shoes of a field polemember are generally located near one or more ends of the core startingat or near a coil region and terminating at the pole face. In someembodiments, the term “pole shoe” can be described generally as a“stator region.”

As used herein, the term “soft magnetic composites” (“SMCs”) refers tothose materials that are comprised, in part, of insulated magneticparticles, such as insulation-coated ferrous powder metal materials thatcan be molded to form an element of the stator structure of the presentinvention.

As used herein, the term “transition region” refers to an optionalportion of a pole shoe that facilitates offsetting or diverting asegment of a flux path (e.g., within a core region) to another segmentof the flux path (e.g., within a pole shoe). One or more pole shoes canimplement transition regions to improve motor volumetric utilization byplacing coils in a compact configuration nearer to an axis of rotation).Specifically, the transition region keeps the reluctance of the fieldpole member relatively low while facilitating compaction of the elementsconstituting an electrodynamic machine. Such elements include shafts,field pole members, magnets and the like.

Discussion

FIG. 2A is an exploded view of an exemplary rotor-stator structure inaccordance with a specific embodiment of the present invention. FIG. 2Adepicts a rotor assembly 261 including at least two cylindrical magnets226 a and 226 b mounted on or affixed to a shaft 225, each ofcylindrical magnets 226 a and 226 b having magnet surfaces (or at leastportions thereof) 224 a and 224 b, respectively, that are cylindrical.In various embodiments of the present invention, shapes other thancylinders, such as cones, can be implemented to practice rotor-statorstructure 250. FIG. 2A also depicts field pole member 205 a, 205 b, and205 c respectively having pole faces 209 a, 209 b, and 209 c forconfronting portions of magnet surface 224 a. Note that not all polefaces are shown or identified.

In various embodiments, each of field pole members 205 is configured toincrease torque generated per unit size (or per unit weight) forelectric motor implementations by at least minimizing the length ofmagnetic flux paths through field pole members. Further, field polemembers 205 provide straight or substantially straight flux paths (orsegments thereof) to minimize linear deviations of the magnetic flux.Typically, the path segments are generally parallel to the axis ofrotation. So by implementing straight or substantially straight paths,each of those field pole members provide a relatively low reluctanceflux path as compared to conventional magnetic return path designs thatrequire magnetic flux to turn sharply about the periphery, such as at anangle of ninety-degrees (or thereabout), between field pole regions. Assuch, rotor-stator structures in some embodiments can implement straightor substantially straight paths to enable electrodynamic machines tooperate with reduced magnetic losses and increased efficiency. Variousalternate embodiments and features of the rotor-stator structure of thepresent invention are described next. The following description isapplicable to magnets having other shapes than or equivalents to conicaland/or cylindrical magnet shapes.

FIG. 2B is an exploded view of an exemplary rotor-stator structure inaccordance with a specific embodiment of the present invention. In thisexample, rotor-stator structure 200 includes a rotor assembly 202 and anumber of active field pole members 204 (i.e., active field pole members204 a, 204 b, and 204 c), whereby active field pole members 204 areconfigured to magnetically couple to and drive magnets of rotor assembly202. Rotor assembly 202 includes two conical magnets 220 a and 220 bmounted on or affixed to a shaft 222 such that at least a portion of aconical magnet surface 221 a on conical magnet 220 a faces at least aportion of a conical magnet surface 221 b on conical magnet 220 b. Inparticular, the smaller-diameter ends (i.e., nearest the cones'vertices, if present, or nearest the cones' conceptual vertices ifotherwise not present due to, for example, truncation of the cone) ofthe conical magnets 220 a and 220 b face each other. Further, conicalmagnets 220 a and 220 b are each positioned adjacent to one group ofends of active field pole members 204. In various embodiments of thepresent invention, conical magnet surfaces 221 a and 221 b each have anangle of inclination with respect to the axis of rotation, where theangle is from about 5 degrees to about 85 degrees. In a specificembodiment, the angle of inclination can be from about 10 degrees toabout 80 degrees. In at least one embodiment, the angle of inclinationis about 30 degrees with respect to the axis of rotation, for example,when conical magnets 220 a and 220 b are composed of relatively highperforming magnet material (e.g., magnets having relatively high valuesof maximum energy product and “Br,” and high coercivity, as is discussedbelow). In various embodiments, shaft 222 can be composed ofmagnetically permeable material, while in other embodiments it can bemade of non-magnetic and/or non-electrically conductive materials. Assuch, rotor-stator structure 200 does not require shaft 222 to form fluxpaths; active field pole members 204 and conical magnets 220 a and 220 bare sufficient to form flux paths in accordance with at least oneembodiment of the invention.

Each of active field pole members 204 includes a field pole member 206and an insulated coil 208 wrapped around a respective field pole member206. Field pole members 206 are positioned coaxial about an axis ofrotation, which can be defined by the axis of shaft 222. Coils 208 a,208 b and 208 c are generally wound about the central portions of fieldpole members 206 a, 206 b and 206 c, respectively, to produce ampereturn-generated magnetic flux in field pole members 206 when the coils208 are energized with current. In at least one embodiment, one or moreactive field pole members 204 constitute, at least in part, a statorassembly (not shown). At each end region of active field pole members204 are pole faces 207, each of which is located adjacent to andconfronting at least a portion of the conical magnet surfaces of theconical magnets 220 a and 220 b, thereby defining functional air gapsbetween magnet surfaces (or portions thereof) and pole faces. Accordingto a specific embodiment of the present invention, pole faces 207 arecontoured to mimic the surfaces of a magnet, such as that of conicalmagnet 220 a. For example, pole face 207 b is a concave surfaceresembling the curvature of that of a convex surface of conical magnet220 a. In one embodiment of the present invention, an optional extendedend, such as an extended end 211 b, extends longitudinally from fieldpole members 206 to extend over and/or past outer surfaces of conicalmagnets 220 a and 220 b. As another example, extended end 217 b isconfigured to extend past the outer surface of conical magnet 220 b forinsertion into one of grooves 242 to construct rotor-stator structure200. But note that in some embodiments, extended end 211 b as well asother extended ends of field pole members 206 are absent, therebypermitting pole faces 207 to confront conical magnets 220 a and 220 bthat have their larger diameter ends (one of which coincides with or isnearest outer magnet surface 223 a) extending to or beyond a radialdistance associated with the outer surfaces of field pole members 206.

As either rotor assembly 202 or the number of active field pole members204 can be configured to rotate in relation to the other, rotor-statorstructure 200 can optionally include bearings 230 and both a frontmounting plate 240 and a rear mounting plate 248. In a specificembodiment, mounting plates 240 and 248 can be made of non-magneticand/or non-electrically conductive materials. Cavities 244 in mountingplates 240 and 248 are designed to receive bearings 230, and grooves 242are designed to receive at least a portion of an extended end, such asextended end 2176, of an active field pole member. In some cases,grooves 242 confine the movement of active field pole members 204 tomaintain a proper position with respect to rotor assembly 202. Aprotective housing (not shown) can be added to protect both rotorassembly 202 and field pole members 204 and can also serve as a heatsink for one or more coils 208. While useful to implement the exemplaryrotor-stator structure 200, various embodiments of the invention are notlimited to including mounting plates 240 and 248 as well as bearings 230and grooves 242, especially when generating a flux path in accordancewith embodiments of the present invention.

Note that although each field pole member 206 is shown to be wrapped byinsulated coil 208, fewer than all of field pole members 206 can bewrapped by coil 208, according to a specific embodiment. For example,coils 208 b and 208 c can be omitted from active field pole members 204b and 204 c, respectively, to form an electrodynamic machine that, forexample, costs less to manufacture than if coils 208 b and 208 c wereincluded. Without coils 208 b and 208 c, members 204 b and 204 cconstitute field pole members rather than active field pole members.Also note that although field pole members 206 a, 206 b and 206 c areshown as straight field pole members, there is no requirement that fieldpole members 206 a, 206 b and 206 c be straight or substantiallystraight. In some embodiments, one or more of field pole members 206 a,206 b and 206 c can be shaped to implement transition regions, such asdescribed below, in field pole members to convey flux in other than astraight flux path. For example, field pole members 206 a, 206 b and 206c can be shaped to position coils 208 closer to shaft 222, therebydecreasing the volume of an electrodynamic machine implementingrotor-stator structure 200.

In at least one specific embodiment, each of one or more active fieldpole members 204 include only one or more coils 208 and a field polemember, such as any of 206 a, 206 b and 206 c. In some cases, activefield pole members 204 can include tape, paper, and/or paint, or thelike that do not add substantial support for coil windings that arewound about a field pole member. Generally, the windings of one or morecoils 208 are wound directly on the field pole member itself. Theconductors of one or more coils 208 can generally include insulation.But in this specific embodiment, each of active field pole members 204does not include any other intermediate structure, such as a coilcarrier structure, which requires additional material cost and laborduring a manufacturing process.

FIG. 3 depicts an end view 300 of rotor-stator 200 illustratingorientation of the pole faces that are configured to interact via an airgap with a confronting magnetic surface of conical magnet 220 a,according to one embodiment of the present invention. Absent from FIG. 3is front mounting plate 240, bearings 230 and conical magnet 220 a, allof which are omitted to depict the end views of both the active fieldpole member and coil shapes, as well as the field pole gaps (“G”)between the field poles. As shown, coils 208 a, 208 b, and 208 crespectively encompass field pole members 206 a, 206 b and 206 c to formactive field pole members 204 a, 204 b and 204 c, all of which arecompactly positioned to increase the packing density of a motor orgenerator implementing rotor-stator structure 200 (as compared toconventional motors using coil windings that typically are wound usingslots 108 of FIG. 1). FIG. 3 also depicts edges of extended ends 311 a,311 b, and 311 c, and pole faces 307 a, 207 b, and 207 c of respectiveactive field pole members 204 a, 2046 and 204 c. Pole faces 307 a, 207b, and 207 c are positioned to form magnetic air gaps between each ofthose pole faces, or surfaces, and at least a portion of the conicalmagnet surface of conical magnet 220 a. Further, field pole gaps aredefined by the sides (or edges) of the field pole members thatconstitute active field pole members 204 a, 204 b and 204 c. Forexample, gap “G” represents any of the field pole gaps as defined, forexample, by planes 310 and 320 extending from sides of respective fieldpole members 206 b and 206 c (FIG. 2B). In at least one specificembodiment, a surface area associated with each of pole faces 307 a, 207b, and 207 c is dimensioned. to generate maximum torque output in anoptimal configuration. An example of such a configuration is one wheremagnetic coupling between conical magnet 220 a and field pole members206 a, 206 b and 206 c is at or near a maximum amount while leakageacross gap “G” between the field pole members is at or near a minimalamount. Note that by increasing the surface area of any of pole faces307 a, 207 b, and 207 c, magnetic coupling is increased.

FIG. 4 depicts another end view 400 of rotor-stator 200 and conicalmagnet 220 a positioned adjacent to pole faces 307 a, 207 b, and 207 c(FIG. 3) in accordance with an embodiment of the present invention. Asshown, outer magnet surface 223 a of conical magnet 220 a is visible, asare the protruding edges of extended ends 311 a, 311 b, and 311 c andcoils 208. Note that while this example shows conical magnet 220 a as adipole magnet (e.g., a permanent magnet) having a north pole (“N”) and asouth pole (“S”), conical magnet 220 a can have any number of northpoles and south poles. Note that in some embodiments, conical magnets220 a and 220 b can be implemented using electro-magnets. Also, FIG. 4defines three sectional views. The first sectional view, X-X, cutsstraight through as a centerline bisecting field pole member 206 a andcoil 208 a and then passes via magnet 220 a through a field pole gapbetween other field pole members 206 b and 206 c. A second section view,Y-Y, bisects field pole member 206 a and coil 208 a and then passes viamagnet 220 a through field pole member 206 b and coil 208 b. A thirdview section view, Y′-Y′, which is similar to the second section view,Y-Y, bisects field pole member 206 a and coil 208 a and then passes viamagnet 220 a through field pole member 206 c and coil 208 c. Sectionview X-X is shown in FIG. 5A, whereas views Y-Y and Y′-Y′ producesimilar drawings, both of which are depicted in FIG. 5B.

FIGS. 5A and 5B depict sectional views illustrating an exemplarymagnetic flux path, according to at least one embodiment of the presentinvention. FIG. 5A depicts a cross section of active field pole member204 a of rotor-stator structure 500, the cross section showing asectional view X-X of coil 208 a and field pole member 206 a. In thisexample, active field pole member 204 a includes pole faces 307 a and505 b, pole shoes 507 a and 507 b, a coil region 506 and coil 208 a. Inview X-X of FIG. 5A, conical magnets 220 a and 220 b are diametricallymagnetized in opposite directions and are positioned adjacent torespective pole shoes 507 a and 507 b of field pole member 206 a.Correspondingly, pole face 307 a of pole shoe 507 a forms a magnetic airgap 551 a with at least a portion 521 a of magnet surface 221 a of FIG.2B, with portion 521 a confronting pole face 307 a and shown as across-section. Similarly, pole face 505 b of pole shoe 507 b forms amagnetic air gap 551 b with at least a portion 521 b of magnet surface221 b of FIG. 2B, with portion 521 b confronting pole face 505 b andshown as a cross-section. Note that portions 521 a and 521 b need notextend the axial length of conical magnets 220 a and 220 b,respectively. For example, portions 521 a and 521 b can be defined byregions that are bounded between the largest and smallestcross-sectional diameters of conical magnets 220 a and 220 b, but can beof any size. Accordingly, portions 521 a and 521 b need only form airgaps with a pole face, with other surface portions of conical magnets220 a and 220 b being configured not to form air gaps, according to atleast one embodiment. Further, coil 208 a encloses a coil region 506 offield pole member 206 a, whereby coil region 506 is definedapproximately by the axial length of coil 208 a surrounding a portion offield pole member 206 a. Absent in FIG. 5A is a depiction of one or morefield interaction regions, which can encompass a space larger than anair gap, such as air gap 551 a, and can extend into, for example,conical magnet 220 a.

In at least one embodiment of the present invention, at least one ofmagnet portions 521 a and 521 b of surfaces on respective conicalmagnets 220 a and 220 b can be defined as being bounded by an angle ofinclination (“.theta.”) 501, which is an angle with respect to an axisof rotation. In the example shown, the axis of rotation is coterminouswith shaft 222. In a specific embodiment, angle of inclination(“.theta.”) 501 is 30 degrees from shaft 222. But note that angle 501can be any angle.

With opposite polarizations, conical magnet 220 a is polarized with itsnorth pole (“N”) pointing in direction 502, and conical magnet 2201) ispolarized with its north pole (“N”) pointing in direction 504. In someembodiments, conical magnets 220 a and 220 b are diametricallymagnetized in exactly opposite directions (i.e., 180 degrees betweendirections 502 and 504). But in other embodiments, directions 502 and504 can be offset to any angle between those directions other than 180degrees, for example, to reduce detent torque (“coping”). In a specificembodiment, directions 502 and 504 are offset to an angle between fromabout 150 degrees to about 180 degrees. In various embodiments, conicalmagnets 220 a and 220 b (or other types of magnets) are each polarizedto have a direction of polarization in one or more planes that aresubstantially perpendicular to the axis of rotation.

FIG. 5B depicts cross sections of active field pole member 204 a andeither active field pole member 204 b or active field pole member 204 cof FIG. 3, and depicts a magnetic flux path, according to one embodimentof the present invention. For ease of discussion, only view Y-Y will bediscussed. View Y-Y is a sectional view of coil 205 a and field pole 206a passing though coil 208 b and field pole member 206 b. Magnetic fluxpath 560 passes through both field pole members 206 a and 206 b andthrough both conical magnets 220 a and 220 b. For purposes ofillustration, magnetic flux path 560 (or flux path) may be described ascomprising two flux paths that are combined by the principle ofsuperposition. Conical magnets 220 a and 220 b form the first flux path(i.e., permanent magnet-generated flux), whereas flux developed byamp-turns of the coil form the second flux path (i.e., ampereturn-generated flux). In this example, magnet flux as the first fluxpath exits the north pole (“N”) of conical magnet 220 a and crosses airgap 551 a to enter pole face 307 a (FIG. 3), the north pole coincidingwith surface portion 521 a, which. confronts pole face 307 a. The firstflux path then traverses longitudinally through field pole member 206 aand. then exits pole face 505 b at the end of field pole member 206 aadjacent to conical magnet 220 b. The first flux path continues bycrossing air gap 551 b and enters the south pole (“S”) of conical magnet220 b, the south pole generally coinciding with a surface portion 521 bof magnet surface 221 b and confronts pole face 505 b. The first fluxpath passes through conical magnet 220 b to its north pole, whichgenerally coincides with a surface portion 561 b of magnet surface 221 bthat confronts pole face 213 b. Next, the first flux path crosses airgap 551 c and enters pole face 213 b (FIG. 2B). From there, the firstflux path returns through field pole member 206 b to pole face 207 bfrom which it exits, crosses air gap 551 d, and then enters the southpole of conical magnet 220 a, thereby completing the first flux path.Generally, the south pole of conical magnet 220 a coincides with asurface portion 561 a of magnet surface 221 a (FIG. 2B) that isconfronting pole face 207 b. Note that in the case shown, the fluxexiting pole face 207 b is equivalent to that flux exiting pole face 207c. Note that no supplemental structure or material need be required toform any portion of magnetic flux path 560. As such, rotor-statorstructure 550 does not include back-iron.

In a specific embodiment, the diameters of conical magnets 220 a and 220b are set so that the length of the flux path in each of conical magnets220 a and 220 b is relatively large with respect to the four air gaps551 a to 551 d, thereby establishing a favorable magnet load line. Notethat each of the four air gaps 551 a to 551 d provides for a fluxinteraction region to facilitate magnetic flux interaction between (orthrough) pole faces and the magnet. Note further that a flux path ineither conical magnet 220 a or 220 b is shown to align along the axis ofmagnetization (i.e., from the south pole to the north pole), which cancontribute to low magnet manufacturing costs and to magnets that cangenerate a relatively high output torque per unit volume (or size). Thecoercivity of the magnet, which is the property of the magnet thatdetermines how well a magnet will keep its internal flux alignment inthe influence of strong external magnetic fields, can be optimallyselected by using appropriate magnet materials for a specificapplication.

In at least one embodiment, rotor-stator structure 550 (FIG. 5B)generates at least a portion of magnetic flux path 560 that extendssubstantially linearly from about surface portion 521 a of the magnetsurface of first conical magnet 220 a to about surface portion 521 b ofthe magnet surface of second conical magnet 220 b. In one instance, theportion of the magnetic flux path consists essentially of surfaceportion 521 a of first conical magnet 220 a, surface portion 521 b ofthe second conical magnet 220 b, at least one of the field pole members,such as field pole member 206 a, and two or more air gaps, such as airgaps 551 a and 551 b.

In at least one embodiment of the present invention, conical magnets 220a and 220 b can have at least the following two magnetic properties.First, conical magnet 220 a and 220 b are able to produce magnetic flux,such as measured in terms of flux density, “B,” with CGS units of Gauss.“CGS” refers to units described in terms of the centimeter, the gram,and the second. Second, the magnet materials of conical magnet 220 a and220 b are such that the magnets resist demagnetization. Materials thathave an ability to highly resist demagnetization are often described ashaving “high coercivity,” as is well known in the art. Suitable valuesof demagnetizing fields can be used to drive a specific magnet materialflux density output to zero. As such, magnet materials that haverelatively high values of coercivity generally indicate that a magnetmaterial is capable of withstanding large values of adverse externalmagnetic field intensities without suffering demagnetization effects. Ina specific embodiment, conical magnet 220 a and 220 b are composed ofmagnet materials having a recoil permeability value relatively close to1.00 and sufficient coercivity, Hd, under operating conditions as to bereliable in reasonably expected conditions of operation.

Magnet materials are often characterized in part by a maximum energyproduct of such materials. In addition, magnet materials may becharacterized by “Br,” which is the magnetic flux density output from amagnet material when measured in a closed circuit and no measuredexternal magnetic fields are being applied to that magnetic material.That maximum flux density value is frequently denoted as “Br.” A highvalue of Br indicates that a magnet material is capable of largemagnetic flux production per pole area (i.e., a high flux density). Inat least one embodiment, conical magnets 220 a and 220 b use magnetshaving high flux production capability (e.g., having high values of“Br”) in configurations where relatively high torque is desired inrelatively small device volumes.

In various embodiments, conical magnets 220 a and 220 b (or othermagnets) use high-valued Br magnets that can be relatively short in theaxial direction and use a cone angle of about 30 degrees, for example,from the axis of rotation. But in some embodiments, conical magnets 220a and 220 b (or other magnets suitable for practicing the presentinvention) use magnet materials having lower cost and lower values ofBr. In this case, the magnets generally are implemented with an air gaphaving a relatively larger area than those associated with higher valuesof Br. In particular, an increased area for an air gap is formed byincreasing the axial length of a magnet, thereby increasing the surfacearea of a magnetic surface confronting a respective pole face. As such,lesser cone angles (e.g., less than 30 degrees) in a same outer diameterdevice (e.g., motor housing) can be used, albeit longer in the axialdirection. Although the output torque performance, and Km, can remainthe same over many embodiments, the manufacturing cost can be less inthe low-valued Br version even though there can be an increase in axiallength.

While various embodiments of the present invention cover a multitude ofdesign motor and/or generator designs using any of known availablemagnet materials, at least one embodiment uses magnet materials with lowratios of values of B to values of adverse applied field intensity, H,such ratios, as is typically specified in many magnet material datasheets, being measured at the respective material's Br point, thoseratios defining the “recoil permeability at Br” of such materials. Whilein some cases magnet materials need not only be limited to high valuesof coercivity, the magnet materials should exhibit predictable outputflux densities when subjected to expected adverse magnetic field orthermal conditions. As such, the value of “recoil permeability” can beat least one factor when designing motors and/or generators using arotor-stator structure of the present invention.

Recoil permeability is generally an expression of the relationshipbetween values of B and the values of adverse applied field intensity.The values of recoil permeability are typically evaluated in terms ofCGS units (because the permeability of air is 1.0 in CGS units) and canbe determined by dividing a value of B (e.g., expressed in Gauss), nearor at Br, by a value of adverse applied field intensity (e.g., H, nearor at Hc, expressed in Oerstead). For some magnet materials, an averagerecoil permeability value can be determined and may be useful in magnetmaterial selection. In one embodiment, recoil permeability can bedefined for various magnetic materials by Magnetic Materials ProducersAssociation (“MMPA”) Standard 0100-00, as maintained by theInternational Magnetics Association (“IMA”). Note that recoilpermeability can also be described in terms of MKS units (i.e., meter,kilogram, and second).

Generally, values of recoil permeability are not less than one whenexpressed in CGS units, The closer that a recoil permeability value isto 1.0, however, the higher the coercivity can be for a specificmeasured material. In most embodiments of the present invention, a valueof recoil permeability is typically less than 1.3. Typicalhigh-coercivity magnet materials, such as magnets composed ofneodymium-iron (“NdFe”) and variants thereof, can have a recoilpermeability value of about 1.04 in CGS units. Examples of recoilpermeability values from various suppliers are as follows: 1.036 forgrade 32H (as manufactured by Hitachi, Ltd.); 1.028 for grade 35H (asmanufactured by Magnetic Component Engineering, Inc. or “MCE”); and 1.02for grades 22H through 33H as well as 1.05 for grades 35SA through N52(as manufactured by Shin-Etsu Magnetics Inc.). An example of such avariant is Neodymium-Iron-Boron, or “NdFeB.” Common low-cost ceramicmagnets, such as those composed of ferrite ceramic, can have a ratiovalue of about 1.25, which permits ceramic magnets to perform adequatelyin most applications. Note that the average recoil permeability oftypical high performance ceramic magnets is usually within a range of1.06 to 1.2 in CGS units, more or less. Example values from onesupplier, Hitachi, Ltd., are as follows: 1.2 for isotropic grade YBM 3and 1.06 for anisotropic grades YBM 1 and 2. Permanent magnets invarious embodiments of the present invention can comprise any magneticmaterial known to those ordinarily skilled in the art. Examples of suchmagnet materials include one or more rare-earth magnet materials thatare known in the art, such as Neodymium iron Boron (“NdFeB”), SamariumCobalt (“SmCo”) and variants of both, as well as ceramic magnets.

Coils 208 wound around each of field pole members 206 form the secondflux path. In this example, the flux generated by the ampere-turns incoils 208 a and 208 b of FIG. 5B travels in a similar path to thepermanent magnet flux, with the exception that conical magnets 220 a and220 b (FIG. 2B) and cylindrical magnets 226 a and 226 b (FIG. 2A) haveeffective properties similar to that of air as viewed by the ampereturn-generated flux. As such, the ampere-turn flux generated withinfield pole member 206 a (e.g., within coil region 506) is present at thepole faces adjacent to conical magnets 220 a and 220 b of FIGS. 5A and5B and cylindrical magnets 226 of FIG. 2A. Note that coils 208, asconductors, can be wires having a circular cross-section or any othershape, such as square or rectangular.

In at lease one specific embodiment, coils 208 can include foilconductors that are conductors having a rectangular cross-section with arelatively large width and a relatively small height. Foil conductorswith insulation between layers can be used in place of wire to decreasewinding resistance and increase current handling capacity in the sameavailable winding volume. Use of a foil conductor can also decrease theinductance of the winding. In one embodiment, the insulation is affixedto one side of the foil to isolate the foil conductor in subsequentwindings around the core. That is, only one side of the foil conductorsneed be insulated since that one side insulates a non-insulated side ofa previous wound portion of the foil conductor (or foil coil).Advantageously, this reduces the amount of insulation required for coils208, thereby saving resources, increasing packing density and increasingthe number of ampere turns (while decreasing the number of conductorturns) in a space otherwise filled by fully insulated conductors (i.e.,insulated on all sides, such as an insulated wire). As the foilconductor also provides for relatively smaller bending radii, it canthereby decrease the winding resistances usually common in conductorshaving sharper bends. By decreasing the resistance, this type ofconductor can also conserve power in generating amp-turn flux,especially in battery-powered motor applications.

FIG. 5C depicts an example of a second flux path exiting a pole face ofthe active field pole member that generates that ampere-turn magneticflux, according to one embodiment of the present invention. In thisfigure, ampere-turn (“AT”)-generated flux is generated in active fieldpole member 204 a and then exits from pole face 513 a of FIG. 5C (or asshown as pole face 505 b in FIG. 5B) while dividing approximately inhalf to form flux 570 a and 570 b. Then, ampere-turn flux 570 a enterspole face 213 b, and ampere-turn flux 570 b enters pole face 513 c.Then, respective portions of the second flux path then travellongitudinally through the other field pole members (e.g., field polemembers 206 b and 206 c) to the other ends of those other field polemembers to return to active field pole member 204 a, which initiallygenerated the second flux path.

FIG. 5D depicts an example of the second flux path(s) returning to apole face of the active field pole member that generated the ampere-turnmagnetic flux, according to one embodiment of the present invention. Asshown, ampere-turn magnetic flux 570 c and 570 d exit respective polefaces 207 b and 207 c to enter pole face 307 a, thereby completing themagnetic circuit of the second flux path (i.e., the ampere-turn magneticflux path).

Conceptually, the magnetic fields generated by the ampere-turns in eachfield pole member of active field pole members 204 a, 204 b, and 204 cin FIG. 5D can be viewed as regions of magnetic potential at each of thepole faces at the end regions or pole shoes of the active field polemembers. In the air gaps between the confronting surfaces of the conicalmagnets and their adjacent pole faces, the flux of the first flux pathand the flux of the second flux path interact in a manner familiar tothose skilled in the art, where such an interaction is useful togenerate torque by an electric motor implementing rotor-stator structure200, according to at least one embodiment of the present invention. Thefirst and the second flux paths of rotor-stator structure 200 areefficient, at least in part, because the flux is contained within thecore regions 506 (FIG. 5A) of field pole members 206 by the currentsrunning through coils 208. The magnet flux generated by each of theconical magnets 220 a and 220 b interacts in a flux interaction regionwith the magnetic flux from pole faces of active field pole members 204.As such, flux leakage paths are generally limited to relatively verysmall regions at pole shoes 507 a and 507 b (FIG. 5A), both of whichinclude the sides and the backs of field pole members 206. As the firstand second flux paths are also mostly straight in the magneticallypermeable material of field pole members 206, these field pole membersare well suited to be implemented with anisotropic (e.g.,grain-oriented), magnetic materials in an efficient manner. As such,field pole members 206 can be composed of any anisotropic, magneticmaterials capable of carrying higher flux densities and loweringmagnetic losses in the direction of magnetic orientation, such as alongthe grains of grain-oriented materials, as compared to the use ofisotropic, non-grain oriented, magnetic materials.

To illustrate, consider that an exemplary anisotropic (e.g.,grain-oriented) material can have a magnetic saturation value of atleast 20,300 Gauss, whereas a typical isotropic lamination material canhave a saturation value of 19,800 Gauss. An example of a suitableanisotropic material for practicing at least one embodiment of theinvention is grade M6 material, as defined by the American Iron andSteel Institute (“AISI”). An example of an isotropic material is M19material, as designated by AISI. Moreover, the anisotropic materialrequires only 126 Oerstead of applied field to reach saturation comparedto the isotropic material, which requires 460 Oerstead. Core losses forthe anisotropic grain-oriented material (e.g., laminations of 0.014 inchthick) can be about 0.66 Watts per pound at 60 Hz with 15,000 Gaussinduction for Flat-Rolled, Grain-Oriented, Silicon-Iron Steel. Bycontrast, a typical isotropic material such as AISI lamination materialM19 can have core losses of about 1.72 to 1.86 Watts per pound undersimilar conditions (e.g., at thicknesses of 0.0185 inches). In view ofthe foregoing, the use of anisotropic materials in forming field polemembers 206 is advantageous over the use of isotropic materials.According to at least one embodiment, a relatively straight shape forfield pole members 206 enables effective use of anisotropic materials,unlike magnetic flux paths of traditional motors.

Unlike output torque generation of conventional motors, the outputtorque generated by rotor-stator structures 200 of various embodimentsof the present invention need not be proportional to the radius from theaxis of rotation of shaft 222 to the active air gaps 551 a to 551 d(FIG. 5B). All other factors being the same, increasing the radialdistance of the pole faces and air gaps from shaft 222 does not changethe output torque in the way that traditional motor design formulasindicate. For example, traditional motor design concepts teach that theregions carrying ampere-turn flux should be designed to have lowreluctance paths, including the part of the ampere-turn magnetic fluxpath that is the air gap. According to various embodiments of thepresent invention, the ampere-turn flux path has a relatively highreluctance path through the space occupied by permanent magnets, such asconical magnets 220, yet peak torque production is relatively high incomparison to that of most traditional motors of the same size or weight(again, with other factors being equal). In a specific embodiment, themagnet materials that constitute conical magnets 220 a and 220 b of FIG.2B and/or cylindrical magnets 226 of FIG. 2A, have a magnet permeabilityvalue similar to that of air, and as such, the volume of each conicalmagnet 220 a and 220 b or cylindrical magnet 226 appears as anadditional air gap to the ampere-turn magnetic circuit. In at least oneembodiment, the output torque generated by an electrodynamic machine isproportional, in whole or in part, to the volumes of conical magnets 220a and 220 b or to the volumes of cylindrical magnets 226.

In operation of rotor-stator structure 200, coils 208 are sequentiallyenergized to cause rotation of rotor assembly 202. The energized coilsgenerate magnetic potentials at the pole faces. These magneticpotentials tend to re-orient the internal field directions of themagnets (e.g., conical magnets 220) to the direction of the appliedexternal field. The external field, in effect, presents anangularly-directed demagnetizing field to conical magnets 220 a and 220b such that the demagnetizing field is capable of reaching relativelylarge amplitudes when a motor implementing rotor-stator structure 200 isunder high torque loads. The intense demagnetizing field candetrimentally re-magnetize magnet materials of conical magnets 220 a and220 b that have insufficient coercivity. For this reason, at least oneembodiment of the present invention uses magnet materials suited forhigh torque loading and have: (1) a low B-to-adverse-applied-fieldintensity ratio, and (2) a relatively low recoil permeability, such asless than 1.3 in CGS units, for example.

In an embodiment of the present invention, the produced torque isthrough the natural inclination of the magnets, such as conical magnets220, to seek the lowest energy position. Accordingly, the magnet polesof conical magnets 220, which can be permanent magnets, tend to rotatetoward regions of greatest magnetic attraction and away from regions ofmagnetic repulsion, whereby such regions of “magnetic potential” arecreated at the air gaps at both ends of energized active field polemembers 204 by the ampere-turn generated magnetic fields. Since a magnethaving a relatively high coercivity will resist attempts to angularlydisplace the direction of its internal magnetic field, this resistanceto angular displacement is manifested as mechanical torque on the bodyof the permanent magnet, thereby transferring torque to the shaft. Assuch, the magnets (e.g., conical magnets 220) can develop and thentransfer torque to the shaft as useful output torque applied to a load.

FIGS. 5E and 5F depict sectional views illustrating an exemplarymagnetic flux path for another rotor-stator structure that includescylindrical magnets, according to at least one embodiment of the presentinvention. FIG. 5E depicts a cross section of active field pole member586 a of rotor-stator structure 580, the cross section showing asectional view X-X of field pole member 586 a and cylindrical magnets590 a and 590 b. While the pole faces, pole shoes, a coil region andcoil are similar in functionality to similarly-named elements of FIG.5A, field pole member 586 a includes an additional structural and/orfunctional element. Namely, field pole member 586 a includes atransition region 588, the function and structure of which are describedbelow, such as in one or more of FIGS. 17A to 20. FIG. 5F depicts asectional view of at least two active field pole members similar to FIG.5B, and depicts a magnetic flux path, according to one embodiment of thepresent invention. Similar to sectional view Y-Y, as defined in FIG. 5B,rotor-stator structure 592 is a sectional view of field pole 586 a andfield pole member 586 b. Magnetic flux path 594 passes through bothfield pole members 586 a and 586 b and through both cylindrical magnets590 a and 590 b. Also shown are transition regions 588. Note that theshaft, pole faces, pole shoes, coil regions and coils are similar infunctionality to similarly-named elements of FIG. 5B.

FIGS. 6A, 6B and 6C illustrate an end view 600 of another exemplaryrotor-stator structure, according to another embodiment of the presentinvention. FIGS. 6A and 6B show end views 600 of a rotor-statorstructure while FIG. 6C is a partial sectional view A-A of FIG. 6B. FIG.6A shows active field pole members 604 each having a skewed pole face607 at an end of a respective field pole member 606. Each skewed poleface 607 has a contoured surface that generally tracks the surfacecharacteristics of that of a confronting surface portion of an adjacentmagnet, such as conical magnet 220 a, to form an air gap having, forexample, a relatively constant air gap thickness. Air gap thicknessgenerally refers to the orthogonal distance between a point on a poleface and a point on a confronting surface of a magnet. The skewed polefaces 607 are, at least in part, defined by surface edges and/or sidesof field pole members 606 that are slightly angled or skewed withrespect to the magnetization direction, (e.g., direction ofpolarization), of an adjacent magnet. Skewed edges and/or sides areshown in FIG. 6A as first skewed edges 650 and second skewed edges 652,both of which are configured as edges of field pole members 606 to formskewed field pole gaps 660 when active field pole members 604 arearranged in a rotor-stator structure. As an example, consider that firstskewed edge 650 c is configured to form an angle 622 with respect to atleast one direction of polarization 630 of a magnet (not shown).Consider further that second skewed edge 652 b is configured to form anangle 620 with respect to direction of polarization 630. Angles 620, 622can be the same angle or can be any other angle that is suitable forforming field pole gaps 660 that are skewed in relation to thedirections of polarization of one or more magnets. Note that FIG. 6C isa partial sectional view showing skewed edges being configured so thatthe plane of magnetic polarization 631 does not align with either offield pole edge 650 or field pole edge 652. In particular, field poleedge 650 c and field pole edge 652 b both do not align (i.e., areskewed) relative to plane of magnetization 631. In at least oneembodiment, field pole edge 650 a and field pole edge 652 are eachparallel to a first plane that is at an angle with a second plane thatincludes or is parallel to plane of magnetization 631.

FIG. 6B is an end view 670 showing skewed pole face edges at both endsof field pole members 606. By implementing skewed field pole gaps 660 ofFIG. 6A in a rotor-stator structure, detent torque (“coating”) isreduced. In at least one embodiment, skewed field pole gaps 660 areadapted for use with permanent magnets that are diametrically polarized,such as conical magnets 220. In this instance, end view 670 of FIG. 6Bis an end view showing pole faces 607 that are configured to havesurface contours similar to that of an adjacent conical magnet 220 a,pole faces 607 being similar to those shown in FIG. 6A. Also shown inFIG. 6B are first skewed edges 680 and second skewed edges 682, whichare associated with pole faces at the other end of field pole members606 (e.g., at the other pole shoe opposite than that associated withfirst skewed edges 650 and second skewed edges 652 as indicated by thebroken lines). First skewed edges 680 and second skewed edges 682 inthis case have angles similar to those of first skewed edges 650 andsecond skewed edges 652, respectively, but face a magnet surfaceassociated with conical magnet 220 b, for example. As such, the angulardirections of the field pole gaps formed by edges 650 and 652 areopposite in the angular direction of the field pole gaps formed by edges680 and 682. Consequently, the diametrically polarized magnets willgenerally not align with a field pole gap having pole face sides similarto those that form field pole gap “G” between planes 310 and 320 (FIG.3), which can be a source of coping torque in an electric motor. Notethat distance between edges 650 and 652, as well as between edges 680and 682, can be configured to be as narrow as necessary to minimize thecoating effects of the field pole gaps. In at least one embodiment,first skewed edges 680 and second skewed edges 682 can have anglessimilar to those of first skewed edges 650 and second skewed edges 652.But edges 680 and 682 lie in the same respective planes as edges 650 and652. Advantageously, this helps to balance torque that tends to twistthe shaft, and also to balance axial forces that derive from thedirection of magnet polarization relative to the skewed edges of fieldpole members 606.

FIGS. 7A and 7B illustrate an exemplary field pole member, according toone embodiment of the present invention. Although each of field polemembers 206 a, 206 b, and 206 c can be composed of a single piece ofmagnetically permeable material (e.g., a piece formed by a metalinjection molding process, forging, casting or any other method ofmanufacture), these field pole members can also be composed of multiplepieces, as is shown in FIGS. 7A and 7B. FIG. 7A depicts one of fieldpole members 206 as a stacked field pole member 700 composed of a numberof laminations 704 integrated together. In this instance, stacked fieldpole member 700 has an outer surface 702 having a cylindrical outsidediameter with an arc and a relatively straight inner surface 706 toincrease the coil packing density while still leaving room for therotating shaft. Field pole member end regions 720 generally include polefaces 707 for interacting with the flux of permanent magnets at each endof field pole member 700, whereas a central portion 722 (i.e., a centralfield pole member portion) generally includes a core region between polefaces 707, such as coil region 506 (FIG. 5A). A coil (not shown) can bewound more or less about central portion 722. FIG. 7B is a perspectiveview of stacked field pole member 700 and laminations 704, which can becomposed of an anisotropic material. In this example, the anisotropicmaterial includes grain-oriented material.

In at least one embodiment, a field pole member 700 includes a centralfield pole member portion 722 having an outer peripheral surface, suchas outer surface 702. The outer peripheral surface is generallycoextensive with a portion of a circle 730 about the axis of rotation,regardless of whether the field pole is composed of laminates. Byforming the outer peripheral surface of a field pole member to fitwithin a circle or an equivalent shape, a more compact rotor-statorstructure provides an electrodynamic machine with a smaller volume thanif the outer peripheral surface coincided with a portion of a square,for example. As depicted in FIG. 7A, a field pole member 700 includeslaminations and a central field pole member portion 722 between a firstflux interaction surface (e.g., a pole face 707) and a second fluxinteraction surface (e.g., the other pole face 707). In this example,outer surface 702 is circumscribed by at least a portion of a circle730, whereby one or more points (e.g., points 740 a and 740 b) intersector touch circle 730. In at least one embodiment, the structure of fieldpole member 700 can be described in reference to a conceptual medianplane, which appears as medial line 710. Medial line 710 extends in anaxial direction and divides a quantity of laminations constituting fieldpole member 700 approximately in half (e.g., includes percentages from50/50 to 60/40). With respect to one side of medial line 710, thelaminations generally decrease in at least one dimension as thelaminations are positioned farther from medial line 710. Note thatalthough not required, the laminations can be formed from a substratecomposed of a magnetically permeable material in configurations thathelp reduce wastage of the magnetically permeable material. But again,wastage need not necessarily be a required factor in the design of eachembodiment of laminated field pole of the present invention.

FIG. 7C shows an example of at least a central portion of a field polemember, according to at least one specific embodiment of the presentinvention. Note that pole shoes having contoured pole faces are omittedso as not to obscure the depiction of cross-sections for at least thecentral portion of a field pole member. Field pole member 790 is formedfrom laminations 792 and is configured to have a square-shaped formfactor to increase field pole cross-sectional area, which in turnincreases an amount of magnetic flux can pass through field pole member790. For example, square cross-sectional area 794 can carry moremagnetic flux than the oval-like shaped cross-sectional area of fieldpole member 700 of FIG. 7A. FIG. 7C also shows a tear-dropcross-sectional area 796 that can be implemented in at least oneembodiment. In particular, tear-drop cross-sectional area 796 lies in aplane having a substantially radial direction. This orientationfacilitates the accommodation of field pole members 790 as the quantityof field pole members 790 increases. Tear-drop cross-sectional area 796can be configured to optimize the ratio of a winding (e.g., copperconductor) to the material (e.g., iron) constituting field pole members790 within a specific set of magnetic flux requirements and the envelopeconstraints of the motor.

Note also that various winding patterns can be implemented in any of thefield poles in FIGS. 7A to 7C to enhance performance. For example, acantered or full-coverage winding can cover substantially all of thesides and/or the back of field pole member 700, at both ends of thestructure, to reduce the flux that might leak from one field pole memberto another. As such, the wire of a coil need not be wound in planesgenerally perpendicular to the long axis of the field pole member, butat an oblique angle. With coils being placed close to the magnetic airgap, those coils can be more effective in reducing flux leakage, forexample, in pole shoe regions. Note that the above-described windingpatterns are applicable to any of the field pole members describedherein.

FIGS. 7D and 7E illustrate another exemplary field pole member,according to another embodiment of the present invention. Althoughsimilar to FIG. 7A, FIG. 7D depicts one of field pole members 586 a and586 b (FIG. 5F) as a stacked field pole member 770. As shown, field polemember 770 is composed of a number of laminations 774 integratedtogether. Field pole member end regions 780 generally include pole faces773 for interacting with the flux of permanent magnets at each end offield pole member 770, whereas a central portion 777 (i.e., a centralfield pole member portion) generally includes a core region between polefaces of field pole members 586 a (FIG. 5E). At ends 780, which can besynonymous with pole shoes in some embodiments, field pole member 770includes transition regions 776. These transitions regions are describedbelow in more detail. FIG. 7E is a perspective view of stacked fieldpole member 770 and laminations 774, which can be composed of ananisotropic material. In this example, the anisotropic material includesgrain-oriented material.

FIG. 8 illustrates another exemplary field pole member having skewedpole faces, according to a specific embodiment of the present invention.As shown, stacked field pole member 800 is constructed from a number oflaminations 804, similar to stacked field pole member 700. Laminations804 are patterned to provide skewed pole faces 807. Pole face 807 isbound by both a first skewed edge 850 and a second skewed edge 852,whereas the other pole face 807 at the other pole shoe is bound by afirst skewed edge 880 and a second skewed edge 882. Note that edges 850,852, 880 and 882 can respectively correspond to edges 650, 652, 680, and682 of FIG. 6B. Also note that edges 850 and 882 can be formed to lie inthe same planes as edges 880 and 852, respectively, to balance torquethat might twist the shaft and also to balance axial forces that derivefrom the direction of magnet polarization relative to the skewed edgesof field pole members 800. In some cases, laminations 804 (as well aslaminations 704) advantageously can be formed (e.g., stamped out) in aseries of either similarly or differently patterned shapes from a singlesubstrate (e.g., a sheet of metal or the like) or from differentsubstrates in a manner that minimizes waste during manufacturing. Asubstrate can either be a single sheet or an elongated strip of materialthat, for example, can be rolled from a spool. Note that the manufactureof laminations 704 (FIG. 7B) and 804 (FIG. 8), for example, does notwaste materials typically jettisoned to create circular holes incircular stator structures.

In some embodiments, laminations 704 and 804 can be assembled fromlaminated anisotropic (e.g., grain-oriented) sheet stock with thedirection of magnetic orientation being oriented longitudinally, such asparallel to an axis of rotation. This is so that flux can be easilyconducted axially from one end of the motor to the other. Thelaminations can be electrically insulated from each other, which canreduce eddy current losses. In one embodiment, laminations 704 and 804are composed of grain-oriented steel and provide various field polemembers with high permeability, low loss and/or high saturation levelsin a relatively low cost material. One type of anisotropic materialsuitable for implementing laminations 704 and 804 iscold-rolled-grain-oriented steel, or “CRGO lamination steel.” Toillustrate the advantages of using grain-oriented lamination inaccordance with at least one embodiment, cold rolled grain orientedsteel, such as grade M6 lamination (as designated by AISI) having athickness of 0.014 inches, can have a typical permeability of 50,000while subjected to an applied field of 10,000 Gauss. By contrast, anisotropic laminate steel (e.g., “M19” laminates of 0.0185 inches thick)can have a typical permeability of about 3700, under similar conditions.Note that permeability, as described above, is in terms of directcurrent (“DC”) permeability. Field pole members can be made from manydifferent magnetically permeable materials, such as silicon iron alloys,steel alloys, iron alloys, nickel iron alloys, cobalt nickel alloys,magnetic powdered alloys, soft magnetic composites, and the like,according to various embodiments of the present invention. Soft magneticcomposite materials, which are also known as “SMC materials,” arecomposed of compacted, electrically insulated particles that are alsomagnetically permeable. As such, SMC materials exhibit relatively loweddy current losses when compared to traditional SiFe laminationmaterials at relatively high frequencies. Another significant advantageof SMC materials is its ability to be formed in three dimensions throughuse of properly designed compaction molds and dies.

FIGS. 9A to 9P illustrate examples of other-shaped permanent magnetsthat can be implemented in a rotor-stator structure, according tovarious embodiments of the present invention. Although the magnets shownin FIG. 2B are conical in shape, the term “conical” is intended to beconstrued broadly to include one or more shapes that form one or moresurfaces, or portions thereof, that when coaxially mounted on a shaft,are at an angle to the shaft such that at least one surface, whenextended, would intersect an axis of rotation. So, the term “conicalmagnet” is meant to cover any configuration of magnet that has at leasta portion of a surface that is conical or tapered toward a point coaxialwith, or on, an axis of rotation. For example, at least one type ofconical magnet has one or more surfaces whereby the cross-sections ofthe magnet at each of those surfaces generally (or on average) eitherincrease or decrease progressively along the axial length of the magnet.In at least one specific, embodiment, a relevant dimension fordescribing a portion of conical magnet surface is a surface boundary,such as a contoured surface area that can be oriented in space withrespect to a line. Note that FIGS. 9E, 9K and 9L depictcylindrically-shaped magnets that do not include at least a portion of aconfronting surface (i.e., a surface configured to confront a pole face)that is other than cylindrical. As such, these types of shapes aregenerally not considered within the definition of what is deemed aconical magnet.

FIG. 9A shows a full cone-shaped magnet as an example of a conicalmagnet, whereas FIG. 9B depicts a conical magnet being a truncated conemagnet described as a “frustum of a right circular cone,” which is afrustum created by slicing the top off a right circular cone (e.g., theslice forming an upper base parallel to the lower base, or outersurface, of the right circular conical magnet). Note that other coneangles other than that shown in FIG. 9A are within the scope of thepresent invention. FIG. 9C shows that a conical magnet can includecylindrical portions added to the large diameter end (or, in some cases,to the small diameter end, such as shown in FIG. 9J) to optimizemagnetic flux in the circuit. FIG. 9D illustrates a conical magnet beingof a “stepped” or graduated form. FIGS. 9F and 9G show examples ofalternative shapes suitable for implementing a magnet in accordance withembodiments of the present invention, where a conical magnet can be ahemispherically-shaped magnet. FIGS. 9H and 9I are generalrepresentations showing that conical magnets of various embodiments canhave any type of concave surface and/or any type of convex surface,respectively.

FIG. 9J shows an exemplary conical magnet in accordance with oneembodiment of the present invention. Here, conical magnet 940 includesan outer surface 950 in which a cavity 952 is formed. Cavity 952 isoptional and can be used to house bearings or the like. In someembodiments, cavity 952 extends inside one or more of surfaces 954, 956and 958. Note that cavity 952 can have differing inside dimensions alongits axial length. Conical magnet 940 includes three surfaces: a firstcylindrical surface 954, a conical surface 956 and a second cylindricalsurface 958. In various embodiments, conical magnet 940 can include:fewer or more surfaces, cylindrical surfaces having larger or smalldiameters, steeper or shallower angles of inclination for conicalsurface 956, etc.

FIGS. 9K and 9L show an end view and a side view, respectively, of anexemplary cylindrical magnet, according to one embodiment of the presentinvention. Cylindrical magnet 961 is composed of two cylindrical magnets960 and 962. In this example, cylindrical magnet 962 is disposed (e.g.,inserted) within cylindrical magnet 960. In one embodiment, cylindricalmagnet 962 is composed of Nee magnetic material (or a variant thereof)and cylindrical magnet 960 is composed of a ceramic magnetic material.In some embodiments, cylindrical magnet 962 is absent, thereby forming aring magnet composed of cylindrical magnet 960 (mounting fixtures notshown). In at least one specific embodiment, cylindrical magnet 962 canbe composed of a magnetically permeable material rather than a magnetmaterial. In one embodiment, cylindrical magnet 962 need not extendthrough cylindrical magnet 960, but rather can extend from one end toany axial length within cylindrical magnet 960. FIGS. 9M and 9N show anend view and a side view, respectively, of an exemplary conical magnet,according to one embodiment of the present invention. Conical magnet 971is composed of two conical magnets 970 and 972. In this example, conicalmagnet 972 is disposed (e.g., inserted) within conical magnet 970. Inone embodiment, conical magnet 970 is composed of NdFe magnetic material(or a variant thereof) and conical magnet 972 is composed of a ceramicmagnetic material. In some embodiments conical magnet 972 can becomposed of a magnetically permeable material instead of magnetmaterial. In some embodiments, conical magnet 972 is absent, therebyforming a hollowed conical magnet composed of conical magnet 970(mounting fixtures not shown). In one embodiment, conical magnet 972need not extend through conical magnet 970, but rather can extend fromone end to any axial length within conical magnet 970.

FIGS. 9O and 9P illustrate yet other conical magnets in accordance withyet other embodiments of the present invention. FIG. 9O illustrates apyramidal-shaped magnet as a conical magnet, albeit truncated, formedwith any number of truncated triangular surfaces 978. FIG. 9Pillustrates a conical magnet 980 of at least one embodiment, whereconical magnet 980 includes a truncated pyramidal magnet 990 includingmagnetic regions 992 formed either therein or thereon. Magnetic regions992 include magnet material that is different from that of truncatedpyramidal magnet 990. Each of those magnetic regions 992 can be selectedto have any predetermined polarity. In one embodiment, truncatedpyramidal magnet 990 is four-sided and is composed of a ceramic material(e.g., magnet material), and each magnetic region 992 (two of which arehidden from view) is composed of NdFe magnet material that is formedupon truncated pyramidal magnet 990. In other embodiments, pyramidalmagnet 990 can have any number of sides. In various embodiments,pyramidal magnet 990 is a magnet support and need not be composed of amagnet material, but rather can be composed of magnetically permeablematerial. In some embodiments, a magnet support 990 can be formed ashaving any shape as those shown in FIGS. 9A to 9I, with any number ofmagnetic regions 992 being disposed on magnet support 990. In that case,magnetic regions 992 can be of any shape suitable to be disposed onspecific shapes of magnet support 990. For example, while the FIGS. 9Oand 9P depict conical magnets, the magnet in FIG. 9O can be cylindricalin nature (i.e., with numerous flat surfaces 978 constituting thecylindrical magnet surface, with the end views appearing like a hexagonor some other polygon). As another example, the magnet in FIG. 9P caninclude a cylindrically-shaped magnet support 990 rather thanpyramidal-like shape. Again, other than FIGS. 9E, 9K and 9L, the conicalmagnets that are illustrated in the foregoing are merely examples ofconical magnets of the present invention.

In a specific embodiment of the present invention, conical magnets areanisotropic, diametrically magnetized, and shaped as a truncated conewith about 30 degrees of cone angle relative to an axis of rotation. Theconical and cylindrical magnets, according to some embodiments, arediametrically magnetized in directions that are generally in a planethat is substantially perpendicular to the axis. At least one advantageof these types of magnet configurations is that such diametric conicalmagnets can be magnetized in the same direction as the original magneticorientation of the magnet material, which provides a higher energyproduct for the magnet (i.e., a more powerful magnet). Anisotropicmagnets are also relatively easy to manufacture and have relatively highmagnetic efficiency per unit magnet volume. Another advantage of adiametric (i.e., 2 pole) magnet is that in a motor having three activefield pole members and three phases, there is only one electricalrevolution for each mechanical revolution of the motor. Accordingly, thediametric magnet, in whole or in part, reduces eddy current losses,hysteresis (“core” or “iron”) losses and electrical switching losses ina motor drive circuit. In some embodiments, a conical magnet can: (1)include a steel core instead of being solid magnet material, (2) beconstructed from ring magnets exhibiting good coercivity, (3) beconstructed from arc-segment magnets, (4) be molded directly onto theshaft, (5) be radially polarized, (6) include a hollow core instead ofbeing solid magnet material, or can include any other similarcharacteristics.

FIG. 10 shows a multiple pole magnet, according to one embodiment of thepresent invention. In this example, permanent magnet 1000 is a four-polemagnet being magnetically oriented to have arcuate magnetic paths 1010from south poles (“S”) to north poles (“N”). Other numbers of poles andmagnet orientations are within the scope and spirit of the presentinvention. Further, a multiple pole magnet, such as permanent magnet1000, can be either a monolithic magnet or a non-monolithic magnetaccording to some embodiments. As used herein, the term “monolithic,” asapplied to a permanent magnet, suggests that the permanent magnet iscomposed of integrated magnetic poles, such that the permanent magnet isnon-discrete and is substantially homogenous in structure. As such, amonolithic permanent magnet lacks any physical interfaces between themagnetic poles. A monolithic magnet therefore is composed of continuousmagnet material. By contrast, permanent magnet 1000 can be anon-monolithic magnet composed of separate magnets, with each separatemagnet contributing an outward facing north or south pole, wherebyphysical interfaces exist between the separate subcomponents. As such, anon-monolithic magnet therefore can be composed of contiguous, butnoncontinuous magnet material. In particular, each separate subcomponentincludes continuous magnet material, but the physical interfaces giverise to discontinuities in the magnet material that constitutes themagnet as a whole. Note that the term “monolithic” can also apply tofield pole members and other elements of the various rotor-statorstructures of the present invention. Note that in at least oneembodiment, non-monolithic magnets can include those magnets whereseparate subcomponents are arranged at a distance from each other suchthat they do not contact each other.

FIG. 11A shows a side view of a rotor-stator structure 1100 as analternate embodiment of the present invention. Generally, a quantity ofthree active field pole members efficiently uses a cylindrical volume orspace that is typically available inside the motor or generator. Assuch, “three” active field pole members are generally used to provide arelatively high packing density. But to provide more balanced operation,more than three active field pole members can be used. As shown, sixactive field pole members 1102 are arranged coaxially to and positionedequidistantly about an axis of rotation. Also, a four-pole magnet 1104is positioned adjacent to the pole faces of active field pole members1102. In this instance, four-pole magnet 1104 is a composite ofindividual magnet arc-segments. Rotor-stator structure 1100 can providemore balance magnetically relative to rotor-stator structures thatinclude three active field pole members, because coils of opposingactive field pole members 1102 can generally be excited at the sametime. Other numbers of active field pole members and other even numbersof magnet poles can suitably be combined to implement rotor-statorstructures of the present invention.

FIGS. 11B to 11C illustrate a subset of the variations in the number offield pole members and/or magnet poles, according to various embodimentsof the present invention. FIG. 11B shows a side view of a rotor-statorstructure 1105 having six field pole members 1106 and a two-pole magnet1107, according to one embodiment of the invention. FIG. 11C depicts aside view of a rotor-stator structure 1108 that includes twelve fieldpole members 1109 and a four-pole magnet 1110, according to anotherembodiment of the present invention. Again, rotor-stator structures1100, 1105 and 1108 depict only a few of the many field polemember-magnet pole combinations in accordance with various embodimentsof the present invention.

In at least one specific embodiment of the present invention, anexemplary rotor-stator structure is disposed in an electrical motor togenerate a torque amplitude that depends on at least one or more of thefollowing: the volume of the magnets, the vector directions of theinteracting fields in the flux interaction regions, the flux density influx interaction regions, the area of the air gaps, and the area of thepole faces. So, the higher the flux density produced by the permanentmagnets and the higher the flux density produced by the active fieldpole members, the higher the torque that will be developed untilsignificant saturation is reached in the field pole members. The magnetmaterials of such a rotor-stator structure should have sufficientcoercivity to prevent partial or total demagnetization in an intendedapplication.

FIGS. 12A to 12D illustrate another rotor-stator structure in accordancewith the present invention. FIG. 12A depicts a rotor assembly 1200including at least two cylindrical permanent magnets 1202 a and 1202 bmounted on or affixed to a shaft 1204. As shown, cylindrical magnets1202 a and 1202 b are diametrically magnetized and positioned to havetheir north poles (“N”) pointing in substantially opposite directions.FIG. 12B shows two views of a field pole member 1220 including two polefaces 1224. Note that pole faces 1224 in this example are contoured orshaped so as to mimic the contours of the cylindrical surfaces ofcylindrical permanent magnets 1202 a and 1202 b, thereby providing arelatively uniform air gap thickness for either portions of thecylindrical surfaces or the entire cylindrical surfaces. In variousembodiments, field pole member 1220 can be composed of laminations (notshown) and can have functionality and/or structure as described withrespect to other embodiments. FIG. 12C is an exploded view of anexemplary rotor-stator structure in accordance with a specificembodiment of the present invention. In this example, rotor-statorstructure 1250 is configured to increase torque generated per unit size(or per unit weight) for electric motor implementations by at leastminimizing the length of magnetic flux paths through field pole members.As field pole members 1206 provide substantially straight flux pathsegments therein, linear deviations of magnetic flux can be minimized.Typically, the path segments are generally parallel to the axis ofrotation. Further, rotor-stator structure 1250 can implement field polemembers 1206 that are straight or substantially straight to minimizereluctance of those field pole members. As reluctance is minimized, sotoo are magnetic losses. In the example shown in FIG. 12C, rotor-statorstructure 1250 includes rotor assembly 1200, three active field polemembers 1252 (each of which implements field pole member 1206 and acoil), end plates 1254 and 1256, and bearings 1258. Note thatcylindrical surfaces 1260 (also referred to as magnet surfaces) ofcylindrical magnets 1202 a and 1202 b are used to confront pole faces1224 (FIG. 12B). Such magnet surfaces can be described as beinginterfacial as magnetic flux passes through those surfaces when the fluxenters or exits pole faces 1224. The magnet surfaces, in whole or inpart (i.e., cylindrical portions thereof), define air gaps betweencylindrical surfaces 1260 and pole faces 1224. In at least oneembodiment, pole faces 1224 are contoured to maintain a uniformthickness for each of the air gaps to increase flux interaction betweencylindrical magnets 1202 a and 1202 b (FIG. 12C) and field pole members1206 a, 1206 b, and 1206 c, thereby increasing output torque in apredictable manner. In cases where field pole members 1206 a, 1206 b,and 1206 c are composed of laminates, pole faces 1224 are contoured tomaintain at least a substantially uniform thickness for each of the airgaps.

FIG. 12D shows a side view of a cross-section for field pole member 1220(FIG. 12B) depicting a straight line 1284 that is indicative of astraight flux path segment in field pole member 1220 regardless ofwhether the magnetic flux path passes from either a permanent magnet oran Ampere Turn (“AT”)-generated flux. In various embodiments of thepresent invention, the path over which flux passes is a function, inwhole or in part, of the shape of field pole member 1220. Note thatstraight line 1284 is representative of straight flux paths between polefaces 1224 of field pole member 1220.

FIGS. 13A and 13B illustrate yet another rotor-stator structure inaccordance with at least one embodiment with the present invention. FIG.13A depicts a rotor assembly 1300 including only one magnet, which inthis example, is a cylindrical magnet 1302 mounted on a shaft 1304. Asshown, FIG. 13B is an exploded view of an exemplary rotor-statorstructure in accordance with a specific embodiment of the presentinvention. In this instance, rotor-stator structure 1350 includes rotorassembly 1300, three active field pole members 1352 (i.e., 1352 a, 1352b, and 1352 c), end plates 1354 and 1356, and bearings 1358. In oneembodiment, plate 1354 is a non-magnetic end plate and end plate 1356 isa magnetically permeable end plate for transferring flux between activefield pole members 1352. In some embodiments, end plate 1356 is anon-magnetic end plate and rotor-stator structure 1350 includes aflux-carrying member (not shown) that is magnetically permeable tocomplete the magnet circuit through cylindrical magnet 1302. Theflux-carrying member magnetically couples the other ends of active fieldpole members 1352 at which there are not pole faces. The field polemember implemented as part of active field pole members 1352 is similarin some respects to field pole member 1220 of FIG. 12B and to any one offield pole members 1206 a, 1206 b, and 1206 c of FIG. 12C. But in thisinstance, each of the field pole members of active field pole members1352 includes only one pole face as there is only one permanent magnetwith which to interact. One example of a single pole face is pole face1324. In alternate embodiments, other-shaped magnets can be substitutedfor cylindrical magnet 1302 to implement other configurations ofrotor-stator structure 1350. Further, rotor-stator structure 1350 canadditionally include other features of the various embodiments describedherein.

FIGS. 13C and 13D illustrate still yet another rotor-stator structure inaccordance with at least one embodiment of the present invention. FIG.13C depicts rotor assemblies 1360 and 1364 including only one conicalmagnet each. In particular, rotor assembly 1360 includes a conicalmagnet 1362 mounted on a shaft 1363 such that at least a portion of aconical surface for conical magnet 1362 faces a first axial direction(“AD1”). By contrast, rotor assembly 1364 includes a conical magnet 1366mounted on a shaft 1365 such that at least a portion of a conicalsurface for conical magnet 1366 faces a second axial direction (“AD2”),where the second axial direction is opposite from the first axialdirection. In at least one embodiment, the first axial direction istoward a flux-carrying member (not shown), such as a magneticallypermeable end plate 1356 (FIG. 13B). While rotor assembly 1364 mightgenerate relatively longer flux paths that are less straight than thoseproduced with rotor assembly 1360, such differences can be negligible incertain applications (e.g., in those cases where motor performance isnot a critical requirement). Note that the relative positions at whichconical magnets 1362 and 1366 are mounted on respective shafts 1363 and1365 are merely examples of some of the possible positions. As such,conical magnets 1362 and 1366 each can be positioned anywhere on ashaft, including the center of either shaft 1363 or shaft 1365. FIG. 13Dis an exploded view of an exemplary rotor-stator structure in accordancewith a specific embodiment of the present invention. As shown,rotor-stator structure 1370 includes rotor assembly 1360 (FIG. 13C),three active field pole members 1372 (i.e., 1372 a, 1372 b, and 1372 c)each of which is similar in functionality as those similarly named inFIG. 13B. But three active field pole members 1372 of FIG. 13D includefield pole members that each include only one pole face, whereby each ofthe single pole faces of three active field pole members 1372 arecontoured to confront the conical magnet surfaces of rotor assembly1360. Rotor-stator structure 1370 also includes end plates 1354 and 1356as well as bearings 1358. Further, rotor-stator structure 1370 canadditionally include other features of the various embodiments describedherein.

FIGS. 14 and 15 depict exemplary implementations of more than twoconical magnets in accordance with various embodiments of the presentinvention. FIG. 14 shows that both sets of conical magnets are arrangedto face each other. A first set includes conical magnets 1402 and asecond set includes conical magnets 1406, with both sets being affixedto a shaft 1404. In one embodiment, two sets of field pole members incooperation with pairs of conical magnets of differing diameter can beused to form a compound motor 1400. In particular, compound motor 1400is formed by integrating two or more motors in parallel, such as innermotor 1450 and outer motor 1452. In this example, an inner motor 1450includes conical magnets 1402 and active field pole members 1412,conical magnets 1402 having smaller diameters than conical magnets 1406.Outer motor 1452 includes an inner motor 1450 as well as conical magnets1406 and active field pole members 1410. In one embodiment, conicalmagnets 1402 and 1406 face away from each other and toward oppositeaxial directions. In alternate embodiments, other-shaped magnets, suchas cylindrical, can be substituted for conical magnets 1402 and 1406.

FIG. 15 illustrates that any number of conical magnets 1502 and 1503 canbe arranged on a shaft 1504. In particular, a first set of conicalmagnets 1502 has their conical surfaces facing one axial direction, anda second set of conical magnets 1503 are arranged to have each conicalsurface facing another axial direction, which is a direction 180 degreesdifferent than that faced by conical magnets 1502. According to variousembodiments of the present invention, any number of conical magnets(e.g., any even or odd number) can be arranged on a shaft, in manyorientations or directions, with one or more active field pole membersbeing adapted to interact with those conical magnets. In one embodiment,active field pole members 1504 are included with pairs of conicalmagnets 1502 and 1503 to form any number of motors in series with eachother. For example, series motor 1500 includes three motors sharing thesame shaft 1580. Each motor includes one conical magnet 1502, oneconical magnet 1503, and any number of active field pole members 1504.Series motor 1500 is well suited for use in down-hole drills and pumpswhere high torque in a relatively small diameter is desired and axiallength is of minimal significance. In alternate embodiments,other-shaped magnets, such as cylindrical, can be substituted forconical magnets 1502 and 1503

FIG. 16 depicts an alternative implementation of a rotor-statorstructure having skewed orientations for its field pole members inaccordance with one embodiment of the present invention. Rotor-statorstructure 1600 includes a number of field pole members 1630 arrangedcoaxially about an axis of rotation 1609 and configured to magneticallycouple with magnets 1602 a and 1602 b, both of which are assembled on ashaft 1622. In one instance, magnets 1602 a and 1602 b can have conicalsurfaces facing toward each other. In at least one embodiment, each offield pole members 1630 is “skewed” in orientation to the axis 1609 suchthat a medial line 1640 passing through each field pole member 1630 isat a skew angle 1650 with a plane 1611 passing through axis 1609. Byorienting field pole members 1630 at skew angle 1650 from the axis ofrotation 1609, detent can be reduced. In one specific embodiment, thepole faces of each of field pole members 1630 can be contoured toconfront the surfaces of magnets 1602 a and 1602 b. Note that one ormore field pole members 1630 need not be active field pole members.

FIG. 17A is a cross-sectional view illustrating another rotor-statorstructure in accordance with one embodiment of the present invention. Inthe cross-sectional view of FIG. 17A, which is similar to sectional viewX-X of FIG. 5A, rotor-stator structure 1700 includes a field pole member1702 and conical-shaped magnets 1720 a and 1720 b. Field pole member1702 has a first pole shoe 1707 a and a second pole shoe 1707 b. Firstpole shoe 1707 a is positioned adjacent to at least a portion (e.g., aconfronting portion) of a surface of magnet 1720 a so that a pole face1705 a can be used to form a first flux interaction region therewith.Similarly, second pole shoe 1707 b is positioned adjacent to at least aportion of a magnet surface of magnet 1720 b so that a pole face 1705 bcan be used to form a second flux interaction region therewith. Both ofthe flux interaction regions include air gaps having either a uniformthickness or a substantially uniform thickness. Field pole member 1702also has a central field pole member portion 1706 around which one ormore windings can be wound. Note that FIG. 17A distinguishes specificregions or portions of field pole member 1702 as pole shoes 1707 a and1707 b, transition regions 1709 a and 1709 b, pole faces 1705 a and 1705b, and central field pole member portion 1706, all of which are merelyexemplary and are not to be construed as limiting. As such, otherembodiments of the present invention can include regions and portions offield pole member 1702 that are of other sizes, lengths, proportions,dimensions, shapes, etc. than as described above.

Further, first pole shoe 1707 a and second pole shoe 1707 b includetransition region 1709 a and transition region 1709 b, respectively, tooffset first pole shoe 1707 a and second pole shoe 1707 b (as well aspole faces 1705 a and 1705 b) from central field pole member portion1706. Each of transitions regions 1709 a and 1709 b is configured toreduce the reluctance for a flux path between pole faces 1705 a and 1705b. For example, transition regions 1709 a and 1709 b provide for adecreased reluctance for flux paths through central field pole memberportion 1706 and either first pole shoe 1707 a or second pole shoe 1707b, as compared to traditional field poles that require transitionregions to be orthogonal (i.e., ninety degrees) to either central fieldpole member portion 1706 or first pole shoe 1707 a and second pole shoe1707 b. Generally, the sharper a flux path turns within a field polemember or any like “low reluctance member,” such as at or near a ninetydegree angle, the higher the reluctance is for that flux path. This inturn leads to increased magnetic losses.

To reduce magnetic losses associated with non-straight flux paths,exemplary field pole member 1702 implements transition regions, such astransition regions 1709 a and 1709 b, to provide a transitory flux pathsegment. Transitory flux path segment 1710 facilitates. lowering thereluctance associated with the length of a flux path extending betweenpole faces, such as pole faces 1705 a and 1705 b. As shown in FIG. 17A,transitory flux path (“S2”) 1710 provides for an acute angle 1704 (whichcan be described also by its complementary obtuse angle 1750) from aflux path segment (“S1”) 1708 associated with central field pole memberportion 1706 to transitory flux path (“S2”) 1710. As shown, flux pathsegment (“S1”) 1708 is in a same general direction indicated astransitory flux path (“S2”) 1710, which deviates from the direction ofthat segment 1708 by acute angle 1704. Note that such a deviation canalso be described in terms of an obtuse angle 1750, as should beapparent to ordinarily skilled artisans. In a specific embodiment, acuteangle 1704 can be between approximately 0 and approximately 60 degrees(including both 0 and 60 degrees). Further, a “non-straight” flux pathcan be described as a path having two consecutive segments 1708 and 1710at an angle 1704 between 60 degrees and 90 degrees. In a specificembodiment, a non-straight flux path includes those paths having asubsequent flux path segment deviating at an angle of about ninetydegrees from a precedent flux path segment, where both the subsequentand the precedent flux path segments are consecutive. As such, segment1708 is precedent to segment 1710 (from south to north magnetized fluxpath) and segment 1710 is subsequent to segment 1708. In someembodiments, the term “substantially straight” can refer to straightflux paths (e.g., paths that have no deviation from a straight line) aswell as flux paths that are 60 degrees or less.

In at least one specific embodiment, the term “flux path segment” refersto a line segment extending from one end (or approximately therefrom) ofa region or portion of field pole member 1702 to the other end (orapproximately thereto), the flux path segment being representative of anapproximate magnetic flux path and/or a portion of an interior flux lineextending between magnetic poles (e.g., pole faces). For example, fluxpath segment (“S1”) 1708 extends the approximate length of central fieldpole member portion 1706 and transitory flux path (“S2”) 1710 extendsthe approximate length of transition region 1709 a.

FIG. 17B illustrates a perspective view of a field pole member inaccordance with a specific embodiment of the present invention. Asshown, a field pole member 1702 (FIG. 17A) includes pole faces 1705 aand 1705 b contoured to confront the conical surfaces of conical magnets1720 a and 1720 b. Note that in other embodiments, pole faces 1705 a and1705 b need not be contoured. For example, pole faces 1705 a and 1705 bof FIG. 17A each can lay in a relatively flat plane perpendicular to thepage on which FIG. 17A is illustrated.

FIGS. 18A and 18B depict air gaps according to embodiments of thepresent invention. FIG. 18A illustrates an air gap 1866 shaped by aconical magnet 1860 and a corresponding pole face, which is not shown toavoid obscuring air gap 1866. In this example, each of normal vectors1862 and 1864 originates from a surface portion on the pole face andterminates at a corresponding point on surface portion 1899 on conicalmagnet 1860. For example, a normal vector 1862 c originates at a portionof the pole face, such as at point 1863, and extends to a point onportion 1899 of surface of conical magnet 1860, such as point 1865. Insome embodiments, normal vectors 1862 and 1864 each have the samelengths.

But in some embodiments, lengths of normal vectors 1864 can differ fromlengths of normal vectors 1862. As such, an arc-shaped cross-section1867 defines a first uniform air gap cross-section at a first axialposition, whereas an arc-shaped cross-section 1802 defines a seconduniform air gap cross-section at a second axial position along thelength of an axis (not shown). Normal vectors 1864 lie in the same planeperpendicular, for example, to surface portion 1899, whereas normalvectors 1862 lie in the same plane also perpendicular to surface portion1899. But both planes are different and produce different cross-sectionsof air gap 1866, such as arc-shaped cross-sections 1802 and 1867.

In some embodiments, it may be advantageous to vary the air gapthickness to create, for example, a narrowed air gap at the smalldiameter end of conical magnet 1860 and a widened air gap at the largediameter end of conical magnet 1860 to better control flux conductedacross air gap 1866 to the adjacent field pole (not shown). For example,the lengths of normal vectors 1862 can be longer than normal vectors1864. Accordingly, this creates a wider air gap at arc-shapedcross-section 1802 and a narrower air gap at arc-shaped cross-section1867. In another example, consider that a load line of conical magnet1860 defines a ratio between the length of the air gap (“L_gap”) to thelength of the magnet (“L_magnet”) as L_gap/L_magnet. To control thisratio or to prevent the ratio from changing, air gap 1866 can be madenarrow at the small end of the conical magnet 1860, where magnet lengthL_magnet is relatively short, and can be wider at the large end ofconical magnet 1860 where magnet length L_magnet is relatively longer.The length of the magnet (“L_magnet”) describes a diameter of conicalmagnet 1860 along which magnetic flux traverses from one magnet surfaceto another.

Note that normal vectors originating from and/or terminating at a curvedsurface generally are not parallel to each other in a planeperpendicular to the surface of magnet 1860. For example, normal vector1862 a is not parallel to normal vector 1862 b, both of which originatefrom a pole face surface having a curvature associated therewith. Airgap 1866 includes an outer boundary having an arc-shaped cross-section1867 and an inner boundary having an arc-shaped cross-section 1869. Notethat although only one air gap 1866 is shown, other similar air gaps canbe formed by other pole face surfaces. Those air gaps have been omittedfor sake of simplicity. Also note that normal vectors 1862 and 1864 donot necessarily represent magnetic flux lines in air gap 1866; theirprimary purpose is to describe the physical structure of the air gap.

FIG. 18B illustrates air gaps 1876 a and 1876 b shaped by a cylindricalmagnet 1870 and corresponding pole faces, both of which are not shown toavoid obscuring those air gaps. In this example, each of normal vectors1872 and 1874 originates from a point on a surface portion on the poleface (not shown) and terminates at a corresponding point on surfaceportion 1890 on conical magnet 1870. Generally, normal vectors 1872 andnormal vectors 1874 lay within a first plane (not shown) and a secondplane (not shown), respectively, where both planes are substantiallyperpendicular to an axis. Accordingly, normal vectors 1872 and normalvectors 1874 define a first and a second substantially uniformcross-section. The first and second substantially uniform cross-sectionsform arc-shaped cross-sections and can be of the same size or of adifferent size, depending on the lengths of normal vectors 1872 and1874. For example, when each of normal vectors 1874 is of the samelength, then they form an arc-shaped cross-section 1898 (e.g., having aperimeter defined by points A, B, C and D). In one case, arc-shapedcross-section 1890 provides uniformity in radial directions about anaxis. In another case, when the lengths of normal vectors 1872 and 1874are the same, then the arc-shaped cross-sections formed therefromprovides uniformity in an axial direction, thereby providing for uniformair gap thickness in whole or in part. Note that the normal vectors canalso originate from a magnet surface (not shown) to describe air gaps.In at least one embodiment, surface areas of pole face surfaces can bedimensioned as a function of the peripheral distance, “W,” between fieldpole members (not shown). FIG. 18B shows a surface area 1878 as acrosshatched outer boundary of air gap 1876 b. Surface area 1878 isrepresentative of other surface areas of other air gaps, all of whichcan be similarly dimensioned. The distance, “W,” of FIG. 18B is selectedto provide maximum magnetic coupling between cylindrical magnet 1870 andthe field pole member by maximizing pole face surface areas 1878 whileminimizing leakage between said field pole members associated with airgaps 1876 a and 1876 b by increasing distance, “W.” An optimal value of“W” minimizes magnetic field leakage while providing an increased outputtorque.

FIG. 19 is a cross-sectional view illustrating yet another general fieldpole member configuration in accordance with yet another embodiment ofthe present invention. In the cross-sectional view of field pole member1902, which is similar to sectional view X-X of FIG. 5A, field polemember 1902 is shown to include similar regions or portions as fieldpole member 1702 of FIG. 17A. In this example, field pole member 1902has a first pole shoe 1907 a, a second pole shoe 1907 b, a first poleface 1905 a, a second pole face 1905 b, and a central field pole memberportion 1906, all of which have equivalent functionalities as thosedescribed above. Note that in other embodiments, the regions andportions of field pole member 1902 can be of other sizes, lengths,shapes, proportions, dimensions, cross-sectional areas, etc. than theabove-mentioned.

As shown in FIG. 19, transition region 1909 a includes a transitory fluxpath (“S2”) 1910 for providing an acute angle 1952 from or to a firstflux path segment associated with central field pole member portion1906, such as flux path segment (“S1”) 1908, and for providing the sameor a different acute angle 1950 from or to a second flux path segment,such as flux path segment (“S3”) 1912, that is associated with firstpole shoe 1907 a. In some instances, the angle at which transitory fluxpath (“S2”) 1910 deviates from flux path segments 1908 and 1912 can alsobe defined by an obtuse angle 1953, which is complementary to acuteangle 1952. In some cases, flux path segment (“S1”) 1908 and flux pathsegment (“S3”) 1912 are at respective distances 1918 and 1916 from anaxis of rotation defined by shaft 1960, both segments 1908 and 1912being substantially parallel to shaft 1960. In FIG. 19, flux pathsegment (“S1”) 1908 and transitory flux path (“S2”) 1910 extend theapproximate length of central field pole member portion 1906 andtransition region 1909 a, respectively, whereas flux path segment (“S3”)1912 extends the length of first pole shoe 1907 a (or a portionthereof). Consider that transition region 1909 a provides a transitoryflux path portion for gently transitioning flux from flux path segment1908 (which is at a distance 1918 from an axis 1960 of rotation) to fluxpath segment 1912 (which is at a distance 1916 from axis 1960). Orconsider that transition region 1909 a provides a transitory flux pathportion for gently transitioning flux a radial distance 1901 from axis1960 without 90 degree bends.

FIG. 20 illustrates a flux line 2002 as an example of a portion ofmagnetic flux extending to a pole face 1905 a of field pole member 1902,according to one embodiment. Flux line 2002 is shown to be approximatelyincident to a flux path including flux path segment (“S1”) 1908,transitory flux path (“S2”) 1910 and flux path segment (“S3”) 1912.

Generally, the motor constant (Km) for an electric motor implementingrotor-stator structure 200 (FIG. 2B), or the like, can be set by varyingthe length of the field pole member's core (i.e., the winding region)without materially affecting the other motor characteristics, other thanfor motor length and weight in some cases. For example, by doubling thewinding length while keeping an outside diameter constant, the windingvolume can also be doubled so the number of turns that can be woundwithin the motor doubles. Since motor performance is set byampere-turns, in whole or in part, when the number of turns doubles, thecurrent can be cut approximately in half and still achieve the sameperformance. So, doubling the number of turns of same wire size cancause the winding resistance to increase by a factor of two or so. Sincethe power lost in a motor can be determined by a square of the currenttimes the winding resistance, a reduction in current by a factor of twoand a doubling of the resistance can lead to a halving of the power lossin the winding.

An exemplary method of converting electrical energy to mechanical torqueby using a rotor-stator structure of at least one embodiment of thepresent invention is described as follows. A first element magnetic fluxis produced by an even number of poles of two permanent magnets, wherebythose magnets substantially direct the first element magnetic flux in aradial direction inside and to the pole surfaces of the magnets. Thepermanent magnets are separated axially, but are connected along acommon axis such that the magnet poles are substantially aligned inplanes that include the axis. The magnet poles in the two permanentmagnets are substantially oppositely directed in magnetization whenviewed along the axis, thus completing a magnetic circuit. The firstelement flux is directed in a substantially axial direction through aplurality of low reluctance path elements, the paths being substantiallyparallel to the axis, thus aiding the magnetic flux density in themagnetic circuit. At least one of the low reluctance path elements issubstantially surrounded by a second magnetic flux-producing elementcomposed of current-carrying means surrounding the low reluctance pathelement. The current in the second flux element, when energized, isselectively switchable so as to produce magnetic potentials in regionsof flux interaction at the axial ends of the low reluctance pathelements, such as at the stator surfaces. The switchable magneticpotentials, when energized, either aid or oppose magnetic flux from thefirst element flux source, thereby producing torque in the permanentmagnets in planes perpendicular to the axis. The magnitude of the torqueproduced is a function of the angle between the direction of the firstelement flux and the second element flux. In some embodiments, theregions of flux interaction at the axial ends of the low reluctance pathelements form air gap surfaces that are at an angle relative to theaxis. In alternative embodiments, the regions of flux interaction at theaxial ends of the low reluctance path elements form air gap surfacesthat are parallel to the axis. In a specific embodiment, the coercivityof the permanent magnets as measured by the relative recoil permeabilityis less than 1.3 in CGS units, for example.

As rotor-stator structures and electrical motors can be designed suchthat their functionalities can be simulated and modeled using computingdevices, at least an embodiment of the present invention relates to acomputer-readable medium having computer code thereon for performingvarious computer-implemented operations, such as modeling the conversionof electrical energy to mechanical torque (or the generation ofelectrical energy from mechanical torque). In particular, controlstrategies of the invention may be implemented in software associatedwith a processor. The media and computer code may be those speciallydesigned and constructed for the purposes of the present invention, orthey may be of the kind well known and available to those having skillin the computer software arts. Examples of computer-readable mediainclude hardware devices that are specially configured to store andexecute program code, such as application-specific integrated circuits(“ASICs”), programmable logic devices (“PLDs”) and ROM and RAM devices.Examples of computer code include machine code, such as produced by acompiler, and files containing higher-level code that are executed by acomputer using an interpreter. For example, an embodiment of theinvention may be implemented using Java, C++, or other object-orientedprogramming language and development tools. Another embodiment of theinvention may be implemented in hardwired circuitry in place of, or incombination with, machine-executable software instructions. Further,other embodiments of the present invention include motors usingrotor-stator structures of the present invention that are electricallydriven by well known drive technology, as would be appreciated by thoseordinarily skilled in the art.

According to various embodiment of the present invention, a rotor-statorstructure for electrodynamic machines has an axis and includes a rotorassembly in which is mounted at least two substantially cylindricalmagnets arranged axially on the axis and being spaced apart from eachother, the cylindrical magnets having regions of predetermined magneticpolarization and each having confronting cylindrical magnetic surfacesof principal dimension substantially parallel to the axis, with themagnetic polarizations being in substantially opposite direction. Therotor-stator structure can also include field pole members arrangedcoaxial to the axis and having flux interaction surfaces formed at theends of the field pole members and located adjacent the confrontingmagnetic surfaces, which are generally coextensive with the principaldimension thereof, defining functioning air gaps therewith. Each of thefield pole members is magnetically permeable. Each of the field polemember is substantially straight. The flux interaction surfaces areconfigured to magnetically couple the field pole members to thecylindrical magnets.

In some embodiments, the rotor-stator structure can further comprise ashaft on which the at least two substantially cylindrical magnets areaffixed, the shaft defining the axis and extending through each of theat least two substantially cylindrical magnets. The flux interactionsurfaces can be shaped to maintain a substantially uniform cross-sectionfor each of the air gaps, the substantially uniform cross-section beingan arc-shaped cross-section in a plane substantially perpendicular tothe axis. The flux interaction surfaces can also be shaped to maintainat least two different cross-sections for each of the air gaps to formsubstantially non-uniform cross-sections for each of the air gaps, theat least two different cross-sections each having arc-shapedcross-section of different dimensions in at least two different planesthat are substantially perpendicular to the axis. The substantiallyuniform cross-section is configured to increase flux interaction betweenthe cylindrical magnets and the field pole members, thereby increasingoutput torque. The shape of each of the air gaps can be commensuratewith the substantially uniform cross-section and another substantiallyuniform cross-section, both of which have similar sizes to provide asubstantially uniform thickness for each of the air gaps. The fluxinteraction surfaces each can have a surface area dimensioned togenerate maximum torque output.

In various embodiments, each of the flux interaction surfaces canfurther include a skewed flux interaction surface to skew field polegaps between adjacent field pole members, thereby minimizing detesttorque. The rotor-stator structure can be configured to limit magneticflux paths to traverse only through two of the cylindrical magnets, thefield pole members, the flux interaction surfaces, and the air gaps.Further, the rotor-stator structure can include a coil wound about oneor more of the field pole members to form active field pole members eachof which excludes back-iron, thereby decreasing magnetic losses as wellas decreasing an amount of materials used to manufacture anelectrodynamic machine. In some embodiments, either the field polemembers are configured to rotate about the axis relative to thecylindrical magnets or the cylindrical magnets are configured to rotateabout the axis relative to the field pole members. Each of thesubstantially straight field pole members can be configured to minimizelinear deviations in a flux path extending between a surface portion ofa first flux interaction surface and a surface portion of a second fluxinteraction surface, the path segment terminating at the surfaceportions.

In at least one embodiment, a rotor-stator structure for electrodynamicmachines can include a shaft defining an axis of rotation and having afirst end portion, a central portion and a second end portion. Therotor-stator structure can also include at least a first magnetstructure and a second magnet structure, each having one or more magnetsurfaces. The first magnet structure and the second magnet structureeach is affixed coaxially on the shaft so that the direction ofpolarization of the one or more magnet surfaces for the first magnetstructure are in substantially opposite directions than the direction ofpolarization of the one or more magnet surfaces for the second magnetstructure. The rotor-stator structure includes a plurality of sets ofwindings and a number of field pole members arranged substantiallycoaxial to the shaft, each of the field pole members including a numberof laminations. Each of the field pole members can have a first poleshoe at a first field pole member end and a second pole shoe at a secondfield pole member end. The first pole shoe is positioned to be adjacentto a portion of the first magnet structure to form a first fluxinteraction region and the second pole shoe is positioned to be adjacentto a portion of the second magnet structure to form a second fluxinteraction region. Both of the first flux interaction region and thesecond flux interaction region include air gaps, each of which can havean arc-shaped cross section in a plane perpendicular to at least onemagnet surface from the one or more magnet surfaces. In some cases, thearc-shaped cross section establishes a substantially uniform thicknessfor each of the air gaps and increases flux interaction between the oneor more magnet surfaces and the field pole members, thereby increasingoutput torque.

In one embodiment, the first pole shoe and the second pole shoe eachfurther include flux interaction surfaces having a surface areadimensioned to generate maximum torque output, the surface area beingdimensioned as a function of at least the distances between the fieldpole members to provide maximum magnetic coupling between the one ormore magnet surfaces and the field pole members while at leastminimizing leakage between the field pole members. In some cases, atleast one of the field pole members is a substantially straight fieldpole member configured to provide a substantially straight flux pathbetween the first flux interaction region and the second fluxinteraction region. The first pole shoe and the second pole shoe eachcan further include a skewed flux interaction surface to skew field polegaps between adjacent field pole members, thereby minimizing detenttorque. Each of the field pole members can also have at least a centralfield pole member portion around which a set of the plurality of sets ofwindings is wound.

In one embodiment, each of the first and the second pole shoes caninclude a transition region connecting each of the first field polemember end and the second field pole member end at a nonorthogonal anglewith the central field pole member portion to reduce reluctance for aflux path between the central field pole member portion and either thefirst or the second pole shoe, or both. The transition region includes atransitory flux path for providing an acute angle from or to a firstflux path segment associated with the central field pole member portionand for providing at the same or a different acute angle from or to asecond flux path segment associated with either of the first and thesecond pole shoes. In some instances, both of the acute angles arebetween approximately 0 and 60 degrees. The first magnet structure andthe second magnet structure can each be dipole magnets. As such, onemagnet surface of the first magnet structure has a north pole pointingin a first direction and one magnet surface of the second magnetstructure has a north pole pointing in a second direction. The first andthe second directions can differ by an angle between 150 to 180 degrees.

In one embodiment, the rotor-stator structure can be configured toeither receive electrical power as an electrical current into the atleast one coil for implementing an electric motor or to receivemechanical power as rotational motion about the shaft for implementingan electric generator. In a specific embodiment, the rotor-statorstructure can be configured to implement either a compound motor or aseries motor, or both, if the rotor-stator structure is implementedwithin the electric motor, and is further configured to implement eithera compound generator or a series generator, or both, if the rotor-statorstructure is implemented within the electric generator.

In alternative embodiments, the first magnet structure and the secondmagnet structure each are multipole magnets, where the one or moremagnet surfaces of the first magnet structure include a plurality ofnorth poles and south poles, one of which is pointing in a firstdirection. The one or more magnet surfaces of the second magnetstructure can also include a plurality of north poles and south poles,one of which is pointing in a second direction. The first and the seconddirections can differ by an angle between 150 to 180 degrees. In somecases, the first magnet structure and the second magnet structureinclude separate magnets, each of which has interfaces contiguous withother separate magnets without any intervening structure. In othercases, the first magnet structure and the second magnet structureinclude either one or more cylinder-shaped magnets each having acylindrical surface or one or more cone-shaped magnets each having aconical surface, or both. Note that the one or more magnet surfaces caneach include discrete regions of magnetization. Also, the first magnetstructure and the second magnet structure each can include a magnetsupport configured to support the regions of magnetization at principaldimensions either at an acute angle to the axis or parallel to the axis,the magnet support being affixed to the shaft.

A rotor-stator structure in various embodiments can be implemented as asingle magnet motor, which can include a shaft and a single magnetstructure having one or more magnet surfaces and being affixed coaxiallyon the shaft so that the direction of polarization of the one or moremagnet surfaces extend in one or more planes that each are substantiallyperpendicular to the axis. The rotor-stator structure for the singlemagnet motor also can include field pole members arranged coaxially tothe axis. The field pole members can have flux interaction surfacesformed at one end of each of the field pole members and positionedadjacently to portions of the one or more magnet surfaces that confrontthe flux interaction surfaces, the flux interaction surfaces and theportions of the one or more magnet surfaces defining air gaps. Therotor-stator structure for the single magnet motor includes aflux-carrying member to complete a magnetic circuit through one or moreof the field pole members and the single magnet structure. In someembodiments, the flux interaction surfaces are contoured to maintain asubstantially uniform cross-section for each of the air gaps. Forexample, the substantially uniform cross-section can be an arc-shapedcross-section in a plane substantially perpendicular to the one or moremagnet surfaces. The substantially uniform cross-section provides asubstantially uniform thickness for each of the air gaps and increasesflux interaction between the one or more magnet surfaces and the fieldpole members, thereby increasing output torque.

In a specific embodiment, the flux interaction surfaces each have asurface area dimensioned to generate maximum torque output, the surfacearea being dimensioned as a function of at least the distances betweenthe field pole members to provide maximum magnetic coupling between theone or more magnet surfaces and the field pole members while at leastminimizing leakage between the field pole members. In one embodiment, atleast one of the field pole members is a substantially straight fieldpole member configured to provide a substantially straight flux pathbetween the one end of each of the field pole members and theflux-carrying member. In some cases, each of the flux interactionsurfaces further comprises a skewed flux interaction surface to skewfield pole gaps between adjacent field pole members, thereby minimizingdetent torque. In one embodiment, the single magnet structure is acylindrical permanent magnet and the one or more magnet surfaces arecylindrical surface portions. In another embodiment, the single magnetstructure is a conical permanent magnet and the one or more magnetsurfaces are conical surface portions, wherein the conical permanentmagnet is affixed on the shaft to face either one axial direction or theother axial direction.

A rotor-stator structure in various embodiments can be implemented aseither a compound or series motor or generator that includes a firstsubset of conical magnets having first conical surfaces arranged axiallyon an axis of rotation such that the first conical surfaces face eachother, and a first subset of first field pole members arranged coaxiallyto the axis and having flux interaction surfaces formed at the ends ofthe first field pole members and adjacent to portions of the firstconical surfaces that confront the flux interaction surfaces, the fluxinteraction surfaces and the portions of the first conical surfacesdefining first air gaps. The rotor-stator structure further includes asecond subset of conical magnets having second conical surfaces arrangedaxially on the axis of rotation such that the second conical surfacesface each other, and a second subset of second field pole membersarranged coaxially to the axis and having flux interaction surfacesformed at the ends of the second field pole members and adjacent toportions of the second conical surfaces that confront the fluxinteraction surfaces, the flux interaction surfaces and the portions ofthe second conical surfaces defining second air gaps. It also includes ashaft on which the first and the second subsets of conical magnets areaffixed, the shaft defining the axis of rotation and extending througheach of the first and the second subsets conical magnets. In oneembodiment, the first subset of conical magnets is disposed in parallelwith (e.g., are disposed within) the second subset of conical magnets toform either a compound motor or a compound generator. For example, thefirst subset of conical magnets can be disposed within the second subsetof conical magnets. In another embodiment, the first subset of conicalmagnets is disposed in series with the second subset of conical magnetsto form either a series motor or a series generator.

A rotor-stator structure in various embodiments can include one or morefield pole members each including a central field pole member portionconfigured to accept one or more sets of windings, a first pole shoecoupled to the central field pole member portion, the first pole shoeincluding a first pole face configured to confront a first magnet, and asecond pole shoe coupled. to the central field pole member portion, thesecond pole shoe including a second pole face configured to confront asecond magnet. The first pole face and the second pole face each includea flux interaction surface contoured to form an air gap having asubstantially uniform cross-section. In one embodiment, the fluxinteraction surface is configured to form the substantially uniformcross-section as an arc-shaped cross-section in a plane substantiallyperpendicular to at least a surface portion on either the first magnetor the second magnet. In some cases, a number of normal vectors in theplane extend orthogonally between points on the flux interaction surfaceand points on the surface portion to define the arc-shapedcross-section, the normal vectors each having a substantially uniformlength. In at least one instance, the substantially uniformcross-section provides a substantially uniform thickness for the airgap, the uniform thickness increasing flux interaction either betweenthe first pole face and the first magnet or between the second pole faceand the second magnet, or both, thereby increasing output torque.

In a specific embodiment, the flux interaction surface comprises asurface area dimensioned to generate maximum torque output, the surfacearea being dimensioned as a function of at least the distances betweenthe field pole member and another field pole member to provide maximummagnetic coupling between the first magnet and the second magnet and thefield pole member while at least minimizing leakage between the fieldpole member and the other field pole member. In an embodiment, at leastone of the field pole members is a substantially straight field polemember configured to provide a substantially straight flux path betweenthe first pole shoe and the second pole shoe. The flux interactionsurface can further include a skewed flux interaction surface to skew afield pole gap between the field pole member and the other field polemember, thereby minimizing detent torque. The skewed flux interactionsurface includes a first edge defining a first side of the field polegap and a second edge defining a second side of another field pole gap,whereby the first edge and the second edge maintain angles that do notalign with a direction of polarization of at least one of either thefirst magnet or the second magnet, wherein one first edge of the fieldpole member and one second edge of the other field pole member form thefield pole gap. The flux interaction surface can be shaped to confrontat least a portion of either a cylindrical permanent magnet or a conicalpermanent magnet.

A field pole member in various embodiments can be configured to eitherreduce or eliminate back-iron between the first pole shoe and the secondpole shoe when a coil is wound about the field pole member, therebydecreasing magnetic losses as well as decreasing an amount of materialsused to manufacture an electrodynamic machine. In at least one case,each of the first and the second pole shoes further comprises atransition region coupling each of the first and the second pole shoesat a nonorthogonal angle with the central field pole member portion toreduce reluctance for a flux path between the central field pole memberportion and either the first or the second pole shoe, or both. The fieldpole member can further include laminations. For example, the field polemember can further include laminations such that a medial planeextending in an axial direction divides a quantity of the laminationsapproximately in half so that on one side of the medial plane,laminations generally decrease in at least one dimension as thelaminations are positioned farther from the medial plane. Thelaminations can be formed from a substrate composed of a magneticallypermeable material in configurations that reduce wastage of themagnetically permeable material. In at least one embodiment, the centralfield pole member portion further comprises an outer peripheral surfacecoextensive with a portion of a circle about an axis of rotation todecrease a volumetric dimension of the field pole member.

FIG. 21A illustrates an example of one implementation of an arrangementof field pole members to form a stator structure for electrodynamicmachines, according to at least one embodiment of the invention. Here,diagram 2100 is an end view showing a portion of a stator structureincluding field pole member 2110 a and field pole member 2110 b, both ofwhich are coaxially positioned about a line, such as an axis 2122 ofrotation for an axial-based electrodynamic machine. Further, field polemember 2110 a and field pole member 2110 b can include an exteriorportion 2114 and an interior portion 2116, respectively. In at least onecase, exterior portion 2114 can be an outer-most region of a field polemember, and can be located, for example, external to an arc 2120 and/orat a radial distance farthest from axis 2122, whereas interior portion2116 can be an inner-most region of a field pole member that can belocated, for example, internal to arc 2120 and/or at a radial distancenearest to axis 2122. In one embodiment, field pole member 2110 b can beoriented with respect to field pole member 2110 a to form an overlapportion, an example of which can be illustrated as overlap region 2199,whereby the overlap portion can be configured to include (e.g.,intercept) a plane 2107, such as a reference plane, passing through axis2122 of rotation. In a specific embodiment, field pole member 2110 a canbe oriented to intercept plane 2107 simultaneous (or substantiallysimultaneous) to the overlap portion associated with field pole member2110 b intercepting by plane 2107.

In view of the foregoing, a stator structure including field pole member2110 a and field pole member 2110 b can be oriented to provide for askewed field pole gap (“G”) 2117, whereby one or more portions of skewedfield pole gap 2117 can be formed at an angle “B” between plane 2107 andline 2115, as shown in FIG. 21A. Further, angle “B” of skewed field polegap 2117 can be configured, for example, to form a skewed field pole gap2117 that can reduce or prevent the number of rotation angles over whicha plane 2107 extends from axis 2122 to an exterior boundary, withoutintercepting one or more field pole members. Further, the arrangement offield pole member 2110 a and field pole member 2110 b can ensure thatradial line segment 2102 passes at least through overlap region 2199.

As shown, plane 2107 can include a radial line segment 2102. As usedherein, the term “radial line segment” can generally refer, at least inone embodiment, to a portion of a plane, such as a line segment, thatrepresents an orientation of a portion of the surface of a magnet, suchas a conical magnet, in relation to field pole members, such as fieldpole members 2110 a and 2110 b. A radial line segment, such as radialline segment 2102, can represent a number of incremental magnetelements, which can be depicted as elements 2195 and 2197. Each of theseelements can be composed of a volume, a surface area, or the like, of asurface of a magnet, such as a conical magnet surface. In at least oneembodiment, the incremental magnet elements can each be composed ofinfinitesimally small units of volume or surface area that, for example,confront one or more pole face portions. The incremental magnet elementscan have the same polarization, with at least a proportion of whichbeing oriented toward pole faces (not shown) of the field pole members.Such pole faces, or portions thereof, can be formed in surfaces 2113.For example, one pole face (or a portion thereof) can be formed at ornear exterior portion 2114 and another pole face (or a portion thereof)can be formed at or near interior portion 2116. In at least oneembodiment, the incremental magnet elements, such as elements 2195 and2197, can represent—conceptually or otherwise—a region of peak orhighest magnet flux (e.g. relative to other parts of a magnet) that canbe associated with, for example, a pole of a magnet. In at least oneexample, the peak amounts of magnet flux can originate from a magnethaving symmetrical properties adjacent to a line segment on the magnetthat corresponds to radial line segment 2102. Note that the variousembodiments are not limited to symmetric magnets. As is shown, radialline segment 2102 includes elements 2195 and 2197. Here, elements 2195represent incremental magnet elements that do not face magneticallypermeable material they do not face a field pole member and/or poleface), whereas elements 2197 (shown with “centered dots”) representincremental magnet elements that face magnetically permeable material(e.g., magnetic flux can emanate from elements 2197 at a directionnormal to the surface of each element 2197). As such, a group 2194 ofelements 2197 face field pole member 2110 a, a group 2198 of elements2195 face skewed field pole gap 2117, and a group 2194 b of elements2197 faces field pole member 2110 b.

Accordingly, the portion of the stator structure shown in FIG. 21A canreduce detent, according to at least one embodiment. In a specificembodiment, the portion of the stator structure shown in FIG. 21A canalso reduce the peak magnitudes of detent (e.g., detent torque), and canoptionally distribute the detent torque over rotational positions. Note,too, that skewed field pole gap 2117 can be configured to have a width2118, such as a uniform width or the like, so that the leakage acrossgap “G” between field pole member 2110 a and field pole member 2110 b isat or near a sufficiently reduced amount for a specific performance ofan electrodynamic machine.

In the example shown, field pole member 2110 a and field pole member2110 b can conceptually include respective medial lines 2112 a and 2112b, both of which can be positioned to coincide (or substantiallycoincide) on an arc 2120 located at a radial distance (“RD”) 2162 fromaxis 2122. In this example, medial lines 2112 a and 2112 b can beparallel (or are substantially parallel) to axis 2122 and lie in amedial plane, such as medial plane 2130, which includes medial line 2112a. Here, medial lines 2112 a and 2112 b each appear as a point in FIG.21A, as these lines extend out of the page in a parallel to axis 2122 atleast in one embodiment. Note that, in some embodiments, medial plane2130 (as well as other medial planes not shown) can be positioned toexclude axis 2122 of rotation. Field pole member 2110 a and field polemember 2110 b can be positioned with respect to a reference plane, suchas planes 2104 and 2107. Here, field pole member 2110 a can be orientedso that medial plane 2130 and planes 2104 form an angle A (or anequivalent angle), which is sufficient to form skewed field pole gap2117 at angle B, where B is equal to (or is substantially equal to) theangle of A minus the angle of C (e.g., B=A−C). C represents the anglebetween planes 2104 and 2107.

To illustrate the functionality of the stator structure portion shown inFIG. 21A, consider that radial line segment 2102 represents a series ofmagnet elements along a line segment that are associated with a largeamount of magnet flux (e.g., a peak amount of magnet flux generated byeach magnet element) that originates from a magnet (not shown). Furtherconsider that radial line segment 2102 sweeps in an angular direction2109, which is shown to be clockwise. At a first point in time, radialline segment 2102 coincides with plane 2104, and, thus, is interceptedby field pole member 2110 a. In this case, group 2194 b of elements 2197is absent from the radial line segment (not shown), and these elementscan be illustrated as elements 2195. At a second point in time, radialline segment 2102 sweeps clockwise, transitioning from intercepting bothfield pole members 2110 a and 2110 b, as shown, to intercepting fieldpole member 2110 b. in this case, group 2194 a of elements 2197 isabsent from the radial line segment (not shown), and these elements canbe shown as elements 2195. Overlap region 2199 can thereby ensure thatradial line segment 2102 does not fall within a field pole gap, whichotherwise might contribute to detent. That is, overlap region 2199 canbe configured to position magnetically permeable material of field polemembers 2110 a and 2110 b to face no less than one or more elements 2197as radial line segment 2102 sweeps an entire revolution, so long asother field pole member similar to 2110 a and 2110 b are similarlysituated about axis 2122. Note that surfaces 2113 can include portionsthat constitute pole faces (not shown), or portions thereof, which canbe configured to confront a surface of a magnet, such as a conicalmagnet or a cylindrical magnet. For example, at least one of surfaces2113 can be configured to be coextensive with an acute angle (e.g., anangle less than 90 degrees) in accordance with at least one embodiment.Note, too, that radial line segment 2102 is not limited to beingorthogonal to axis 2122. In at least one instance, radial line segment2102 can be at an angle to axis 2122 such that rotation in direction2109 sweeps out a conical sectional (e.g., in association with theconical surface portion of a conical magnet).

As used herein, the term “overlap” can generally refer, at least in oneembodiment, to a portion of a second field pole member that caninterpose between, for example, an axis 2122 of rotation and a firstfield pole member. In one instance, a portion of field pole member 2110b that is positioned within a conceptual triangular area defined bypoint “m,” point “n,” and the axis of rotation can form an overlapportion. An overlap portion can prevent a plane 2107 that includesradial line segment 2102 from extending beyond an exterior boundary of,for example, the stator structure without intercepting a field polemember. As used herein, the term “medial” can generally refer, at leastin one embodiment, to a plane (i.e., a medial plane) that longitudinallydivides a field pole member into two parts, whereby the two parts can beequivalent (or substantially equivalent) parts. For example, a medialplane can bisect the field pole member into two halves. In at least oneinstance, a medial plane can extend longitudinally in parallel (orsubstantially parallel) to a height dimension of a field pole member(see e.g., FIG. 21E), or along (e.g., within 45 degrees) the samedimension. In a specific embodiment, a medial line can be coincidentwith a centerline passing lengthwise through an approximate center of afield pole member, regardless of whether the field pole member isstraight. An approximate center of a field pole member can be determinedby the center of a cross-sectioned area that is perpendicular to, forexample, a longitudinal dimension (e.g., a length of a field pole memberextending from pole face to pole face). In a specific embodiment, theapproximate center of a field pole member can be an aggregate of thecentroids of each of the cross-sectioned areas.

In various embodiments, other attributes of field pole members 2110 aand 2110 b can be modified to influence the functionality and/orstructure of a stator structure to form a suitable skewed field polegap. For example, while field pole members 2110 a and 2110 b arerepresented as having elliptical cross-sections, field pole members 2110a and 2110 b can have other cross-sectional shapes. For instance, fieldpole members 2110 a and 2110 b can have triangular cross-sections,rectangular cross-sections, rhomboidal cross-sections, trapezoidalcross-sections, crescent-shaped cross-sections and/or surfaces, and anyother shape or modification thereof. Further, while field pole members2110 a and 2110 b are represented as having symmetrical sides and/orlateral portions, field pole members 2110 a and 2110 b can haveasymmetrical sides and/or lateral portions. In one example, the sidesand/or lateral portions of field pole members 2110 a and 2110 b can havesides shaped to have different dimensions, such as different heightdimensions. As another example, one side can be convex while anotherside can be concave. In various embodiments, field pole members 2110 aand 2110 b can be formed as monolithic components composed of magneticpermeable material, or can be formed of constituent elements, such aslaminates. In some embodiments, field pole members 2110 a and 2110 b canbe formed in accordance with U.S. Nonprovisional application Ser. No.11/707,817, entitled “Field Pole Members and Methods of Forming. Samefor Electrodynamic Machines,” published on Sep. 6, 2007 as U.S.Publication No. 20070205675 A1. In at least one embodiment, field polemembers 2110 a and 2110 b can be formed to have uniform cross-sectionsextending, for example, along a length dimension from pole shoe to poleshoe. In a specific embodiment, field pole members 2110 a and 2110 b canbe formed to have substantially uniform cross-sections extending, forexample, along a length dimension (e.g., an axial length) from pole faceto pole face. In at least one embodiment, different field pole memberscan be positioned at different radial distances from an axis of rotation(not shown). In one embodiment, field pole members 2110 a and 2100 b canbe referred to as adjacent field pole members, the structure of whichcan be replicated about axis of rotation 2122.

FIG. 21B illustrates examples of various implementations of field polemembers to form various stator structures for electrodynamic machines,according to various embodiments of the invention. Here, diagram 2140 isan end view showing a portion of a stator structure including field polemember 2161 a and field pole member 2161 b, both of which are coaxiallypositioned about axis 2122 of rotation. Further, field pole member 2161a and field pole member 2161 b can respectively include medial planes2130 a and 2130 b. As shown, medial planes 2130 a and 2130 b extendthrough and include axis 2122 of rotation. As such, the portion of astator structure that is shown in diagram 2140 can establish aneffective field pole gap 2133 in which a plane 2107, which includesradial line segment 2102, can extend through an arc segment, as shown byan angular distance (“AD”) 2191 a, to an exterior region or boundary. Asused herein, the term “an effective field pole gap” can generally refer,at least in one embodiment, to a gap as determined by an angulardistance of an arc segment (or an arc length) in the context of a radialline segment extending into an exterior boundary. In some embodiments,an effective field pole gap can be refer to a sector of a circle boundedby two radii and an arc segment, such as 2191 a, whereby a radial linesegment, such as radial line segment 2102, can extended withoutintersecting a field pole member (i.e., no incremental magnet elementsassociated with the radial line segment confront a pole face, or portionthereof). Note that in this example, each of the incremental magnetelements of radial line segment 2102, such as elements 2195, isattracted toward field pole 2161 a (e.g., due to the illustratedproximity of radial line segment 2102), and, thus, can contribute to atorque in that direction. Since radial line segment 2102 can representthe highest flux region of, for example, a symmetric magnet (not shown),when the torque contributions (e.g., the incremental torque magnitudesand directions) of each of the magnet incremental elements over theentire surface of the magnet (or series of magnets in rotor hubstructure) are summed, the net torque can be in a direction toward fieldpole 2161 a. The peak amplitude of the torque increases as radial linesegment 2102 rotates toward the center of the angular distance (“AD”)2191 a, and, then changes to zero when radial line segment 2102 is at(½) AD (i.e., half the angular distance 2191 a). This torque profilecontinues to a similar peak amplitude, with the torque being directedtoward field pole 2161 b as it continues to rotate (e.g., in theclockwise direction).

Diagram 2141 is an end view showing a portion of another statorstructure that includes field pole member 2163 a and field pole member2163 b, both of which are coaxially positioned about axis 2122 ofrotation. Further, field pole member 2163 a and field pole member 2163 bcan respectively include medial planes 2131 a and 2131 b, neither ofwhich is configured—at least in this example—to extend through andinclude axis 2122 of rotation. As such, the portion of the statorstructure that is shown in diagram 2141 can form an effective field polegap width, as defined by a plane that includes radial line segment 2102and a plane 2171. Note that radial line segment 2102 and plane 2171, andarc segment 2191 b establish a sector of a circle representative of theeffective field pole gap. As such, plane 2107, which includes radialline segment 2102, can extend through an arc segment, as shown by anangular distance (“AD”) 2191 b, to an exterior region or boundary fromaxis 2122. Accordingly, field pole member 2163 a and field pole member2163 b can be oriented to form a skewed field pole gap. Note thatangular distance (“AD”) 2191 b is less than angular distance (“AD”) 2191a, which can reduce detent (i.e., the incremental magnet elements 2195face no field pole members for a shorter duration of time (and/or overfewer rotational positions) in diagram 2141 than in diagram 2141). Thus,the orientation of a skewed field pole gap (and/or a skewed field polegap angle)—in whole or in part—can be configured to modify the angulardistance of an arc segment through which radial line segment 2102 canextend to an exterior boundary to, for example, reduce detent. Further,skewed field pole gap (and/or a skewed field pole gap angle) can beconfigured to include an overlap region, as is shown next in diagram2142, to reduce peak detent torque amplitudes. Note that the incrementalmagnet elements 2195 that face the field pole gap (e.g., do not confronta field pole face) can generate a radial torque. As such, these magnetelements can be attracted to the nearest high permeability surface(i.e., the nearest field pole member). Note, too, that the detent peakamplitude can be reduced if a sufficient quantity of incremental magnetelements is attracted to field pole 2163 b sooner (e.g., in few rotationangles) than in the arrangement shown in diagram 2141. In this fieldpole member arrangement, the detent torque amplitude may spread out,thereby distributing detent torque, as well as elements 2195, over morerotational positions. In some cases, this is because the skewing offield pole members can enable the incremental magnet elements to facethe field pole gap at angles of rotation different than in thearrangement shown in diagram 2141. The portion of the stator structureshown in diagram 2141 can thereby reduce the peak amplitude of detentand “smear out the waveform” (i.e., distribute detent torque amplitudeover more rotational positions than is the case with the in thearrangement shown in diagram 2141).

Diagram 2142 is an end view showing a portion of yet another statorstructure that includes field pole member 2165 a and field pole member2165 b, both of which are coaxially positioned about axis 2122. Further,field pole member 2165 a includes medial planes 2131 a, which is notconfigured—at least in this example—to extend through and include axis2122. The portion of the stator structure that is shown in diagram 2142does not form an effective field pole gap width as a result—in whole orin part of the forming an overlap portion 2103. Thus, the angulardistance (“AD”) of an arc segment is zero or approximately zero. In thisexample, overlap portion 2103 is formed by interposing an interiorportion 2116 between exterior portion 2114 and axis 2122, for example,within a triangular-shaped area 2123. Thus, overlap portion 2103provides for transitioning radial line segment 2102 from field polemember 2165 a to field pole member 2165 b without a plane 2107, whichincludes radial line segment 2102, extending to an exterior boundary. Inthe example shown in diagram 2142, incremental magnet elements thatoverlap either field pole face, such as elements 2197, do not generateincremental torque. Rather, other incremental magnet elements that facethe gap between the field poles members, such as elements 2195, cancontribute to the generation of incremental torques. Again, theincremental torques from incremental magnet elements can be summed todetermine the net detent torque. The result of this summation can dependon the shape of the field pole face (not shown), the total magnet size(not shown), and the like. Generally, at least in some embodiments, thepeak amplitude of the detent waveform can decrease for the field polemember arrangement in diagram 2142, at least in comparison with thearrangement in diagram 2140, which includes non-skewed field polemembers.

FIG. 21C depicts approximate detent torque amplitudes as a function ofvarious rotation angles for the field pole arrangements shown in FIG.21B, according to at least one embodiment of the invention. Diagram 2139illustrates that the field pole member arrangement in diagram 2140, forexample, can produce higher torque amplitudes due to detent than theother field pole member arrangements in diagrams 2141 and 2142. In atleast one embodiment, the other field pole member arrangements indiagrams 2141 and 2142 can respectively reduce the detent torqueamplitudes for a given rotation angle (or a range of rotation angles).In one or more embodiments, the other field pole member arrangements indiagrams 2141 and 2142 also can respectively distribute elements 2195,which do not face a field pole member, over an increased number ofrotation angles (or rotational positions), which, in turn, canfacilitate the reduction in detent torque amplitude.

FIG. 21D illustrates an example of a field pole arrangement that canfacilitate the distribution of incremental magnet elements overadditional rotation angles, according to at least one embodiment of theinvention. Diagrams 2140 a and 2142 a represent at least a portion offield pole member arrangements in diagrams 2140 and 2142, respectively,in FIG. 21B. As shown in diagram 2140 a, radial line segment 2102 ofFIG. 21B can sweep through rotational positions RP1, RP2, and RP3 asradial line segments 2102 a, 2102 b, and 2102 c, respectively.Similarly, radial line segment 2102 of FIG. 21B can sweep throughrotational positions RP1, RP2, and RP3 as radial line segments 2102 d,2102 e, and 2102 f, respectively, as shown in diagram 2142 a. The fieldpole arrangement in diagram 2140 a shows that rotational position RP2includes all of the elements 2197 that face a field pole member, such asfield pole member 2161 a, for the three rotational positions. As such,the elements 2195 at rotational positions RP1 and RP3 can contribute toa corresponding amount of detent torque amplitudes. By contrast, theorientation of field pole member 2165 a distributes elements 2195 and2197 over more rotational positions, which, in turn, can correspond to adistribution of detent torque amplitudes over a larger range ofrotational positions (rotation angles). Diagram 2142 b illustrates avariant of diagram 2142 a in which the cross section of the field polemembers is triangular (or substantially triangular), such as field polemembers 2189 a and 2189 b. Here, radial line segment 2102 of FIG. 21Bcan sweep through rotational positions RP1, RP2, and RP3 as radial linesegments 2102 g, 2102 h, and 2102 i, respectively, as shown in diagram2142 b. The field pole arrangement in diagram 2142 b shows that thetriangular cross sections and/or the positioning of field pole members2189 a and 2189 b can increase the number of elements 2197 forindividual rotational positions, which, in turn, can correspond to adistribution and/or a reduction of detent torque amplitudes over alarger range of rotational positions (rotation angles).

FIG. 21E depicts attributes that can influence detent reduction by astator structure, according to various embodiments of the invention.Here, diagram 2181 depicts a cross-section 2512 of a field pole memberhaving a height dimension, h, which characterizes an elongated dimension(“ED”) of cross section 2512. Cross-section 2152 also has a widthdimension, w, where w<h. Other examples of elongated dimensions (“ED”)and widths (“w”) are depicted in FIGS. 23 and 24. Both the height andwidth dimensions can be modified to, for example, form an overlapportion and/or a skewed field pole gap, at least according to oneembodiment. In at least some embodiments, an elongated dimension can bepositioned to confront an area on a surface that is coextensive (or issubstantially coextensive) with an acute angle with an axis of rotationso as to confront, for example, a conical magnet structure. Toillustrate, consider that the line segment between point m and point nfor field pole member 2210 (FIG. 21) coincides with an elongateddimension. Further, the elongated dimension can be positioned at anangle, such as angle A, with a plane that includes the axis of rotation,such as plane 2104. In at least one example, the angle can beconfigurable to modify a number of rotational positions over which theelongated cross section confronts a pole region of a conical magnet. Thepole region can be oriented parallel (or substantially parallel) to theplane that includes the axis of rotation. In another example, the anglecan be configurable to distribute detent torque over the number ofrotational positions.

Diagram 2183 depicts a cross-section 2514 of a field pole member beingconfigurable to include asymmetric sides. For example, a side 2177 ofcross-section 2154 can have triangular shape, whereas a side 2179 ofcross-section 2154 can have a contoured shape that can either be convexor concave. Note that modifying either side of cross-section 2154 caninfluence the formation of an overlap portion and/or a skewed field polegap, at least according to one embodiment.

FIG. 22 depicts an example of a conical magnet that a stator structurecan be configured to confront, according to at least one embodiment ofthe invention. Here, conical magnet 2200 is shown to be composed ofmagnet portions 2210, which can be substantially flat or can have abevel or curvature, such as shown by arc 2202. As shown, a referenceplane 2220 can include or coincide with a radial line segment 2102 ofFIG. 21A, which can be representative of incremental magnet elementsdisposed, for illustration purposes, within a pole region associatedwith a surface of conical magnet 2200, such as magnet portion 2210 a,with polarization (e.g., flux) in the direction away from the surface ofthe magnet. When conical magnet 2200 is integrated as a rotor thatoperates with a stator structure, the incremental magnet elementsrepresented by radial line segment 2102 can be configured so that someportion of the elements confront pole faces of one or more field polemembers (e.g., including an overlap portion) during rotation.

FIG. 23 illustrates an example of an implementation of field polemembers for forming a stator structure, according to at least oneembodiment of the invention. Here, diagram 2300 is an end view showing aportion of a stator structure including field pole members, includingfield pole members 2310 a, 2310 b, and 2310 c, each of which can becoaxially positioned about axis 2322 of rotation. Field pole members2310 a, 2310 b, and 2310 c can have substantially triangular-shapedcross-sections having differently-shaped sides, as shown. Further, fieldpole member 2310 a and field pole member 2310 b can include an exteriorportion 2314 and an interior portion 2316, respectively. In oneembodiment, field pole member 2310 b can be oriented with respect tofield pole member 2310 a to form an overlap portion (not shown) of fieldpole member 2310 b at interior portion 2316. The overlap portion can beconfigured to include (e.g., intercept) a plane 2302, such as areference plane, and/or a radial line passing through axis 2322 ofrotation. In a specific embodiment, field pole member 2310 a can beoriented to intercept plane 2302 simultaneous (or substantiallysimultaneous) to the overlap portion (not shown) of field pole member2310 h intercepting plane 2302. Medial plane 2350 is representative ofan example of a medial plane that passes through a field pole member,such as field pole member 2310 b, to form a first part and a secondpart. In various embodiments, medial plane 2350 excludes axis 2322. Inat least one embodiment, one or more of the field pole members shown indiagram 2300 can be active field pole members.

Field pole members 2310 a, 2310 b, and 2310 c are each shown in thisexample to include asymmetric sides. For example, field pole member 2310b can include a first side 2330 a and a second side 2330 b, and fieldpole member 2310 c can include a first side 2332 a and a second side2332 b. Here, first sides 2330 a and 2332 a are associated with a firstdimension, and second sides 2330 b and 2332 b are associated with asecond dimension. In the example shown, the first dimension can berepresented by a first height, “h1,” which extends between an exteriorboundary 2380 and an interior boundary 2382, whereas the seconddimension can be represented by a second height, “h2,” which extendsbetween exterior boundary 2380 and interior boundary 2382. The firstheight, h1, is less than the second height, h2, thereby making firstsides 2330 a and 2332 a asymmetric to second sides 2330 b and 2332 b.Note that field pole members 2310 a, 2310 b, and 2310 c can each beassociated with an elongated dimension, ED, and a width, w, according toone embodiment of the invention.

In at least one embodiment, the field pole members shown in FIG. 23 canbe oriented to form a skewed field pole gap (“G”) 2390. In particular,an active field pole member 2310 b can include a side surface portion2360 oriented at a first angle, D, from a reference plane 2302, andanother active field pole member 2310 c can include a side surfaceportion 2370 being oriented at a second angle, E, from reference plane2120. Thus, side surface portion 2360 and side surface portion 2370 canform, for example, a skewed field pole gap portion 2375. Note thatskewed field pole gap portion 2375 can extend a distance equivalent toeither the first height or the second height, or both. In a specificembodiment, skewed field pole gap portion 2375 can have a uniform width2318. In one embodiment, first angle, D, and second angle, E, are thesame (or are substantially equivalent) to form skewed field pole gapangle, which can be shown as either angle D or E. Regardless, skewedfield pole gap portion 2375 and/or skewed field pole gap 2390 can belocated at an angle that prevents a plane or a radial line 2302 fromextending from axis 2322 to exterior boundary 2380. Note that each ofthe sides of the triangular-shaped cross-sections shown in FIG. 23 canbe sized differently, according to one embodiment.

FIG. 24 illustrates an example of another implementation of field polemembers for forming a stator structure, according to one embodiment ofthe invention. FIG. 24 illustrates an example of another implementationof field pole members to form a stator structure for electrodynamicmachines, according to another embodiment of the invention. Here,diagram 2400 is an end view showing a portion of a stator structureincluding field pole members, including field pole members 2410 a, 2410b, 2410 c, and 2410 d, each of which are coaxially positioned about axis2422 of rotation. The field pole members shown in FIG. 24 can havesubstantially triangular-shaped cross-sections having differently-shapedsides, as shown, and can be composed of any number of laminates.Further, field pole member 2410 b and field pole member 2410 c caninclude an exterior portion 2414 and an interior portion 2416,respectively. In one embodiment, field pole member 2410 c can beoriented with respect to field pole member 2410 b to form an overlapportion (not shown) of field pole member 2410 b at interior portion2416. The overlap portion can be configured to include (e.g., intercept)a plane and/or a radial line 2402, such as a reference plane, passingthrough axis 2422 of rotation. In a specific embodiment, field polemember 2410 b can be oriented to intercept a radial line 2402simultaneous (or substantially simultaneous) to the overlap portion offield pole member 2410 b intercepting radial line 2402. Medial plane2450 is representative of an example of a medial plane that passesthrough a field pole member, such as field pole member 2410 d, to dividefield pole member 2410 d into a first part 2450 a and a second part 2450b. In various embodiments, medial plane 2450 excludes axis 2422. In atleast one embodiment, one or more of the field pole members shown indiagram 2400 can be active field pole members. Medial plane 2450 can beat angle (e.g., with respect to a radial line) that does not includeaxis 2422. Note that field pole members 2410 a, 2410 b, 2410 c, and 2410d can each be associated with an elongated dimension, ED, and a width,w, according to one embodiment of the invention.

Field pole members 2410 a, 2410 h, 2410 c, and 2410 d are each shown inthis example to include asymmetric sides. For example, field pole member2410 a can include a first side 2462 and a second side 2460. Here, firstside 2462 can be represented by a first height, “h1,” and second side2460 can be represented by a second height, “h2.” As shown, the firstheight, h1, is shorter than the second height, h2, thereby making firstside 2462 asymmetric to second side 2460. Further, field pole member2410 a can include first side 2462 composed of a first subset 2472 oflaminates, each laminate having substantially uniform heights (e.g.,extending between an exterior boundary and an interior boundary). Fieldpole member 2410 a can also include second side 2460 composed of asecond subset 2470 of laminates having multiple heights (e.g., extendingbetween an exterior boundary and an interior boundary). In at least oneembodiment, the field pole members shown in FIG. 24 can be oriented toform a skewed field pole gap (“G”) 2480. In particular, an active fieldpole member 2410 c can include a first side oriented to confront anadjacent second side of another active field pole member 2410 d. Notethat skewed field pole gap 2480 can have a uniform width 2418. In atleast one embodiment, first subset 2472 of laminates need not includelaminates of uniform height, and second subset 2470 of laminates neednot include different heights for the laminates.

FIG. 25 is a perspective view of a stator structure for electrodynamicmachines, according to one embodiment of the invention. Here, diagram2500 is an perspective view showing a stator structure including fieldpole members, including field pole members 2510, each of which arecoaxially positioned about axis of rotation (not shown). The field polemembers shown in FIG. 25 can have substantially triangular-shapedcross-sections composed of a number of laminates. Further, field polemembers 2510 can include pole faces 2590 configured to confront aconical magnet. As shown, medial plane 2520 can be representative of anexample of a medial plane that passes through a field pole member 2510to form a first part 2522 and a second part 2524. Also shown, is aradial line 2517 associated with a plane passing through the axis ofrotations, whereby the radial line 2517 intercepts a first pole faceportion 2516 and a second pole face portion 2514.

FIG. 26 illustrates an example of yet another implementation of fieldpole members for forming a stator structure, according to yet anotherembodiment of the invention. Here, diagram 2600 is an end view showing aportion of a stator structure including field pole members, each ofwhich can be coaxially positioned about axis 2622 of rotation. The fieldpole members for FIG. 26 can include substantially triangular-shapedcross-sections.

In a specific embodiment, surfaces 2633 can be pole faces (or portionsthereof) associated with pole shoe members, such as pole shoe members2610 a, 2610 b, 2610 c, 2610 d, and 2610 e, that can be integrated withfield pole member cores (not shown). Further, pole shoe member 2610 aand pole shoe member 2610 b can include an interior portion 2616 and anexterior portion 2614, respectively. In one embodiment, pole shoe member2610 a can be oriented with respect to pole shoe member 2610 b to forman overlap portion (not shown) of field pole member 2610 a at interiorportion 2616. The overlap portion can be configured to include (e.g.,intercept) a plane and/or a radial line 2602, such as pole shoe member2610 b can be oriented to intercept plane 2602 simultaneous (orsubstantially simultaneous) to the overlap portion of field pole member2610 a intercepting plane 2602. Medial plane 2650 a is representative ofan example of a medial plane that passes through a pole shoe member,such as pole shoe member 2610 d, to form a first part 2650 a and asecond part 2650 b. In another example, medial plane 2650 b can berepresentative of a contoured medial plane. In various embodiments,medial plane 2650 excludes axis 2622.

Pole shoe members 2610 a, 2610 b, 2610 c, 2610 d, and 2610 e are shownin this example to each include asymmetric sides. For example, pole shoemember 2610 a can include a first side 2671 and a second side 2673.Here, first side 2671 can be formed to include a side portion having afirst contoured surface, such as a convex surface, whereas second side2673 can be formed to include a side portion having a second contouredsurface, such as a concave surface. In the example shown, a convexsurface of pole shoe member 2610 a and a concave surface of pole shoemember 2610 b can include or intercept plane 2602 simultaneously (orsubstantially simultaneously). In at least one embodiment, the pole shoemembers shown in FIG. 26 can be oriented to form a skewed pole shoe gap(“G”) 2680. Note that skewed pole shoe gap 2680 can have a uniform width2618. In a specific embodiment, pole shoe members 2610 a, 2610 b, 2610c, 2610 d, and 2610 e can be formed on field pole cores or members 2692that include a medial plane 2650 c that intercepts axis 2622.

FIG. 27 is a perspective view of a stator structure for electrodynamicmachines, according to one embodiment of the invention. Here, diagram2700 is a perspective view showing a stator structure including fieldpole members each composed of a field pole core 2710 and pole shoemembers 2720. The field pole members can be arranged coaxially aboutaxis of rotation (not shown). The field pole members shown in FIG. 27can have substantially triangular-shaped cross-sections. Further, thefield pole members can include pole faces 2790 configured to confront aconical magnet.

A practitioner of ordinary skill in the art requires no additionalexplanation in making and using the embodiments of the rotor-statorstructure described herein but may nevertheless find some helpfulguidance by examining the following references in order from most toleast preferred: “IEEE 100: The Authoritative Dictionary of IEEEStandard Terms,” Institute of Electrical and Electronics Engineers (KimBreitfelder and Don Messina, eds., 7th ed. 2000), “General MotorTerminology,” as defined by the Small Motor and Motion Association(“SMMA”), and “Standard Specifications for Permanent Magnet Materials:Magnetic Materials Producers Association (“MMPA”) Standard No. 0100-00,”International Magnetics Association.

The foregoing description, for purposes of explanation, used specificnomenclature to provide a thorough understanding of the invention.However, it will be apparent to one skilled in the art that specificdetails are not required in order to practice the invention. In fact,this description should not be read to limit any feature or aspect ofthe present invention to any embodiment; rather any one feature oraspect of one embodiment can be readily interchanged with anotherfeature or aspect in any of the other embodiments. While the abovedescription of the embodiments relates to a motor, the discussion isapplicable to all electrodynamic machines, such as a generator. Thus,the foregoing descriptions of specific embodiments of the invention arepresented for purposes of illustration and description. They are notintended to be exhaustive or to limit the invention to the precise formsdisclosed; obviously, many modifications and variations are possible inview of the above teachings. The embodiments were chosen and describedin order to best explain the principles of the invention and itspractical applications; they thereby enable others skilled in the art tobest utilize the invention and various embodiments with variousmodifications as are suited to the particular use contemplated. As usedherein, the term exemplary is used to describe one of the many examplesof the various implementations and/or embodiments of the invention.Notably, not every benefit described herein need be realized by eachembodiment of the present invention; rather any specific embodiment canprovide one or more of the advantages discussed above. It is intendedthat the following claims and their equivalents define the scope of theinvention.

1. A stator structure for electrodynamic machines comprising: aplurality of field pole members being arranged coaxial to an axis ofrotation, the plurality of field pole members comprising: adjacent fieldpole members being disposed to intersect a common plane that includesthe axis of rotation, the adjacent field pole members comprising: afirst field pole member including a first pole face portion; and asecond field pole member including a second pole face portion, whereinthe first pole face portion and the second pole face portion aresubstantially coextensive with an acute angle to the axis.
 2. The statorstructure of claim 1 wherein at least one of the adjacent field polemembers includes a medial plane positioned at an angle to the commonplane.
 3. The stator structure of claim 1 wherein the adjacent fieldpole members comprise: a first field pole member including a first fieldpole member portion; and a second field pole member including a secondfield pole member portion, wherein the first field pole member portionand the second field pole member portion are positioned to include thecommon plane.
 4. The stator structure of claim 1 wherein the adjacentfield pole members comprise: a first field pole member including a firstpole face portion being disposed at a first subset of one or more radialdistances from the axis; and a second field pole member including asecond pole face portion being disposed at a second subset of one ormore radial distances from the axis, wherein the first pole face portionand the second pole face portion are configured to respectively confronta first radial line segment portion and a second radial line segmentportion at substantially the same time, the first radial line segmentportion and the second radial line segment portion being associated witha magnet having a curved surface, whereby the first radial line segmentportion and the second radial line segment portion rotate in non-planarspace.
 5. The stator structure of claim 1 wherein the adjacent fieldpole members comprise: a first field pole member; and a second fieldpole member positioned with respect to the first field pole member toform an overlap portion in association with the second field polemember, wherein the overlap portion of the second field pole member isconfigured to include the common plane that includes the axis ofrotation.
 6. The stator structure of claim 5 wherein the position ofeither the first field pole member or the second field pole member, orboth, are configurable to form an effective field pole gap between thefirst field pole member and the second field pole member.
 7. The statorstructure of claim 1 wherein the adjacent field pole members eachcomprise a field pole member having a substantially triangular crosssection.
 8. The stator structure of claim 1 wherein the adjacent fieldpole members are formed to have asymmetric sides.
 9. The statorstructure of claim 1 wherein at least one adjacent field pole member ofthe adjacent field pole members comprises: a medial line extending alongthe axial length of the one adjacent field pole member, the medial linebeing either parallel to the axis or at a skew angle to the axis. 10.The stator structure of claim 1 wherein the adjacent field pole membersare active field pole members, and each has substantially uniform crosssections along an axial length.
 11. A stator structure forelectrodynamic machines comprising: a plurality of active field polemembers being arranged coaxial to an axis of rotation, at least one ofthe plurality of active field pole members comprises: at least a portionthat includes an elongated cross section having an elongated dimensionpositioned to confront an area on a surface of a magnet that issubstantially coextensive with an acute angle with the axis of rotation,wherein the elongated dimension is positioned at an angle with a planeincluding the axis of rotation.
 12. The stator structure of claim 11wherein the angle is configurable to modify a number of rotationalpositions over which the elongated cross section confronts a pole regionof a conical magnet, the pole region being oriented substantiallyparallel to the plane including the axis of rotation.
 13. The statorstructure of claim 11 wherein the angle is configurable to distributedetent torque over curved surfaces of the plurality of active field polemembers in three-dimensions for the number of rotational positions. 14.The stator structure of claim 11 wherein the plurality of active fieldpole members further comprises: a first active field pole memberincluding a first side surface portion positioned at a first angle fromthe plane that includes the axis; and a second active field pole memberincluding a second side surface portion being positioned at a secondangle from the plane, wherein the first side surface portion and thesecond side surface portion form a skewed field pole gap portion havinga skewed field pole gap angle that is equivalent to either the firstangle or the second angle, or both.
 15. The stator structure of claim 14wherein the skewed field pole gap angle can be modified to determine anumber of rotational positions over which another plane including aradial line segment can extend to an exterior boundary.
 16. The statorstructure of claim 15 wherein the number of rotational positionsincludes zero.